minecraft-assets/data/minecraft/recipes/cooked_mutton.json

{
  "type": "minecraft:smelting",
  "category": "food",
  "cookingtime": 200,
  "experience": 0.35,
  "ingredient": {
    "item": "minecraft:mutton"
  },
  "result": {
    "id": "minecraft:cooked_mutton"
  }
}