diff --git a/paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftMushroomCow.java b/paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftMushroomCow.java
index bfe39c7a9d..596146ad78 100644
--- a/paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftMushroomCow.java
+++ b/paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftMushroomCow.java
@@ -37,16 +37,24 @@ public class CraftMushroomCow extends CraftCow implements MushroomCow, io.paperm
     @Override
     public boolean addEffectToNextStew(PotionEffect potionEffect, boolean overwrite) {
         Preconditions.checkArgument(potionEffect != null, "PotionEffect cannot be null");
-        MobEffectInstance minecraftPotionEffect = CraftPotionUtil.fromBukkit(potionEffect);
-        if (!overwrite && this.hasEffectForNextStew(potionEffect.getType())) {
+        // Paper start - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta
+        return this.addEffectToNextStew(io.papermc.paper.potion.SuspiciousEffectEntry.create(potionEffect.getType(), potionEffect.getDuration()), overwrite);
+    }
+
+    @Override
+    public boolean addEffectToNextStew(io.papermc.paper.potion.SuspiciousEffectEntry suspiciousEffectEntry, boolean overwrite) {
+        Preconditions.checkArgument(suspiciousEffectEntry != null, "SuspiciousEffectEntry cannot be null");
+        Holder<MobEffect> minecraftPotionEffect = CraftPotionEffectType.bukkitToMinecraftHolder(suspiciousEffectEntry.effect());
+        // Paper end - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta
+        if (!overwrite && this.hasEffectForNextStew(suspiciousEffectEntry.effect())) {
             return false;
         }
         SuspiciousStewEffects stewEffects = this.getHandle().stewEffects;
         if (stewEffects == null) {
             stewEffects = SuspiciousStewEffects.EMPTY;
         }
-        SuspiciousStewEffects.Entry recordSuspiciousEffect = new SuspiciousStewEffects.Entry(minecraftPotionEffect.getEffect(), minecraftPotionEffect.getDuration());
-        this.removeEffectFromNextStew(potionEffect.getType()); // Avoid duplicates of effects
+        SuspiciousStewEffects.Entry recordSuspiciousEffect = new SuspiciousStewEffects.Entry(minecraftPotionEffect, suspiciousEffectEntry.duration()); // Paper - sus effect entry API
+        this.removeEffectFromNextStew(suspiciousEffectEntry.effect()); // Avoid duplicates of effects // Paper - sus effect entry API
         this.getHandle().stewEffects = stewEffects.withEffectAdded(recordSuspiciousEffect);
         return true;
     }
@@ -101,6 +109,43 @@ public class CraftMushroomCow extends CraftCow implements MushroomCow, io.paperm
         this.getHandle().setVariant(net.minecraft.world.entity.animal.MushroomCow.Variant.values()[variant.ordinal()]);
     }
 
+    // Paper start
+    @Override
+    public List<io.papermc.paper.potion.SuspiciousEffectEntry> getStewEffects() {
+        if (this.getHandle().stewEffects == null) {
+            return List.of();
+        }
+
+        final List<io.papermc.paper.potion.SuspiciousEffectEntry> effectEntries = new java.util.ArrayList<>(this.getHandle().stewEffects.effects().size());
+        for (final SuspiciousStewEffects.Entry effect : this.getHandle().stewEffects.effects()) {
+            effectEntries.add(io.papermc.paper.potion.SuspiciousEffectEntry.create(
+                org.bukkit.craftbukkit.potion.CraftPotionEffectType.minecraftHolderToBukkit(effect.effect()),
+                effect.duration()
+            ));
+        }
+
+        return java.util.Collections.unmodifiableList(effectEntries);
+    }
+
+    @Override
+    public void setStewEffects(final List<io.papermc.paper.potion.SuspiciousEffectEntry> effects) {
+        if (effects.isEmpty()) {
+            this.getHandle().stewEffects = null;
+            return;
+        }
+
+        List<SuspiciousStewEffects.Entry> nmsPairs = new java.util.ArrayList<>(effects.size());
+        for (final io.papermc.paper.potion.SuspiciousEffectEntry effect : effects) {
+            nmsPairs.add(new SuspiciousStewEffects.Entry(
+                org.bukkit.craftbukkit.potion.CraftPotionEffectType.bukkitToMinecraftHolder(effect.effect()),
+                effect.duration()
+            ));
+        }
+
+        this.getHandle().stewEffects = new SuspiciousStewEffects(nmsPairs);
+    }
+    // Paper end
+
     @Override
     public String toString() {
         return "CraftMushroomCow";
diff --git a/paper-server/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaSuspiciousStew.java b/paper-server/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaSuspiciousStew.java
index 7a43e326e5..192cd33f62 100644
--- a/paper-server/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaSuspiciousStew.java
+++ b/paper-server/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaSuspiciousStew.java
@@ -21,7 +21,7 @@ public class CraftMetaSuspiciousStew extends CraftMetaItem implements Suspicious
 
     static final ItemMetaKeyType<SuspiciousStewEffects> EFFECTS = new ItemMetaKeyType<>(DataComponents.SUSPICIOUS_STEW_EFFECTS, "effects");
 
-    private List<PotionEffect> customEffects;
+    private List<io.papermc.paper.potion.SuspiciousEffectEntry> customEffects; // Paper - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta
 
     CraftMetaSuspiciousStew(CraftMetaItem meta) {
         super(meta);
@@ -47,7 +47,7 @@ public class CraftMetaSuspiciousStew extends CraftMetaItem implements Suspicious
                     continue;
                 }
                 int duration = effect.duration();
-                this.customEffects.add(new PotionEffect(type, duration, 0));
+                this.customEffects.add(io.papermc.paper.potion.SuspiciousEffectEntry.create(type, duration)); // Paper - use suspicious effect entry for suspicious stew meta
             }
         });
     }
@@ -73,8 +73,8 @@ public class CraftMetaSuspiciousStew extends CraftMetaItem implements Suspicious
         if (this.customEffects != null) {
             List<SuspiciousStewEffects.Entry> effectList = new ArrayList<>();
 
-            for (PotionEffect effect : this.customEffects) {
-                effectList.add(new net.minecraft.world.item.component.SuspiciousStewEffects.Entry(CraftPotionEffectType.bukkitToMinecraftHolder(effect.getType()), effect.getDuration()));
+            for (io.papermc.paper.potion.SuspiciousEffectEntry effect : this.customEffects) {
+                effectList.add(new net.minecraft.world.item.component.SuspiciousStewEffects.Entry(CraftPotionEffectType.bukkitToMinecraftHolder(effect.effect()), effect.duration())); // Paper - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta
             }
             tag.put(CraftMetaSuspiciousStew.EFFECTS, new SuspiciousStewEffects(effectList));
         }
@@ -106,7 +106,7 @@ public class CraftMetaSuspiciousStew extends CraftMetaItem implements Suspicious
     @Override
     public List<PotionEffect> getCustomEffects() {
         if (this.hasCustomEffects()) {
-            return ImmutableList.copyOf(this.customEffects);
+            return this.customEffects.stream().map(suspiciousEffectEntry -> suspiciousEffectEntry.effect().createEffect(suspiciousEffectEntry.duration(), 0)).toList(); // Paper - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta
         }
         return ImmutableList.of();
     }
@@ -114,27 +114,47 @@ public class CraftMetaSuspiciousStew extends CraftMetaItem implements Suspicious
     @Override
     public boolean addCustomEffect(PotionEffect effect, boolean overwrite) {
         Preconditions.checkArgument(effect != null, "Potion effect cannot be null");
+        return addCustomEffect(io.papermc.paper.potion.SuspiciousEffectEntry.create(effect.getType(), effect.getDuration()), overwrite); // Paper - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta
+    }
 
-        int index = this.indexOfEffect(effect.getType());
-        if (index != -1) {
-            if (overwrite) {
-                PotionEffect old = this.customEffects.get(index);
-                if (old.getDuration() == effect.getDuration()) {
+    // Paper start - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta
+    @Override
+    public boolean addCustomEffect(final io.papermc.paper.potion.SuspiciousEffectEntry suspiciousEffectEntry, final boolean overwrite) {
+        Preconditions.checkArgument(suspiciousEffectEntry != null, "Suspicious effect entry cannot be null");
+        if (this.hasCustomEffects()) {
+            final List<io.papermc.paper.potion.SuspiciousEffectEntry> matchingEffects = this.customEffects.stream().filter(
+                entry -> entry.effect() == suspiciousEffectEntry.effect()
+            ).toList();
+            if (!matchingEffects.isEmpty()) {
+                if (overwrite) {
+                    boolean foundMatchingDuration = false;
+                    boolean mutated = false;
+                    for (final io.papermc.paper.potion.SuspiciousEffectEntry matchingEffect : matchingEffects) {
+                        if (matchingEffect.duration() != suspiciousEffectEntry.duration()) {
+                            this.customEffects.remove(suspiciousEffectEntry);
+                            mutated = true;
+                        } else {
+                            foundMatchingDuration = true;
+                        }
+                    }
+                    if (foundMatchingDuration && !mutated) {
+                        return false;
+                    } else if (!foundMatchingDuration) {
+                        this.customEffects.add(suspiciousEffectEntry);
+                    }
+                    return true;
+                } else  {
                     return false;
                 }
-                this.customEffects.set(index, effect);
-                return true;
-            } else {
-                return false;
             }
-        } else {
-            if (this.customEffects == null) {
-                this.customEffects = new ArrayList<>();
-            }
-            this.customEffects.add(effect);
-            return true;
         }
+        if (this.customEffects == null) {
+            this.customEffects = new ArrayList<>();
+        }
+        this.customEffects.add(suspiciousEffectEntry);
+        return true;
     }
+    // Paper end - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta
 
     @Override
     public boolean removeCustomEffect(PotionEffectType type) {
@@ -145,10 +165,12 @@ public class CraftMetaSuspiciousStew extends CraftMetaItem implements Suspicious
         }
 
         boolean changed = false;
-        Iterator<PotionEffect> iterator = this.customEffects.iterator();
+        // Paper start - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta
+        Iterator<io.papermc.paper.potion.SuspiciousEffectEntry> iterator = this.customEffects.iterator();
         while (iterator.hasNext()) {
-            PotionEffect effect = iterator.next();
-            if (type.equals(effect.getType())) {
+            io.papermc.paper.potion.SuspiciousEffectEntry effect = iterator.next();
+            if (type.equals(effect.effect())) {
+        // Paper end - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta
                 iterator.remove();
                 changed = true;
             }
@@ -171,7 +193,7 @@ public class CraftMetaSuspiciousStew extends CraftMetaItem implements Suspicious
         }
 
         for (int i = 0; i < this.customEffects.size(); i++) {
-            if (this.customEffects.get(i).getType().equals(type)) {
+            if (this.customEffects.get(i).effect().equals(type)) { // Paper - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta
                 return i;
             }
         }
@@ -216,7 +238,7 @@ public class CraftMetaSuspiciousStew extends CraftMetaItem implements Suspicious
         super.serialize(builder);
 
         if (this.hasCustomEffects()) {
-            builder.put(CraftMetaSuspiciousStew.EFFECTS.BUKKIT, ImmutableList.copyOf(this.customEffects));
+            builder.put(CraftMetaSuspiciousStew.EFFECTS.BUKKIT, ImmutableList.copyOf(com.google.common.collect.Lists.transform(this.customEffects, s -> new PotionEffect(s.effect(), s.duration(), 0)))); // Paper - add overloads to use suspicious effect entry to mushroom cow and suspicious stew meta - convert back to potion effect for bukkit legacy item serialisation to maintain backwards compatibility for the written format.
         }
 
         return builder;