PaperMC/paper-server/nms-patches/net/minecraft/world/item/crafting/FurnaceRecipe.patch

--- a/net/minecraft/world/item/crafting/FurnaceRecipe.java
+++ b/net/minecraft/world/item/crafting/FurnaceRecipe.java
@@ -4,6 +4,14 @@
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.level.block.Blocks;
 
+// CraftBukkit start
+import org.bukkit.craftbukkit.inventory.CraftFurnaceRecipe;
+import org.bukkit.craftbukkit.inventory.CraftItemStack;
+import org.bukkit.craftbukkit.inventory.CraftRecipe;
+import org.bukkit.craftbukkit.util.CraftNamespacedKey;
+import org.bukkit.inventory.Recipe;
+// CraftBukkit end
+
 public class FurnaceRecipe extends RecipeCooking {
 
     public FurnaceRecipe(MinecraftKey minecraftkey, String s, CookingBookCategory cookingbookcategory, RecipeItemStack recipeitemstack, ItemStack itemstack, float f, int i) {
@@ -19,4 +27,17 @@
     public RecipeSerializer<?> getSerializer() {
         return RecipeSerializer.SMELTING_RECIPE;
     }
+
+    // CraftBukkit start
+    @Override
+    public Recipe toBukkitRecipe() {
+        CraftItemStack result = CraftItemStack.asCraftMirror(this.result);
+
+        CraftFurnaceRecipe recipe = new CraftFurnaceRecipe(CraftNamespacedKey.fromMinecraft(this.id), result, CraftRecipe.toBukkit(this.ingredient), this.experience, this.cookingTime);
+        recipe.setGroup(this.group);
+        recipe.setCategory(CraftRecipe.getCategory(this.category()));
+
+        return recipe;
+    }
+    // CraftBukkit end
 }