Preheat oven to 400°F.
Coat a rimmed baking sheet with nonstick cooking spray.
Combine ground chicken, grated apple, egg, garlic powder, cloves, 3/4 cup breadcrumbs, salt, and black pepper in a large bowl.
Mix well with a spoon or your hands.
If mixture is still wet, add remaining 1/4 cup bread crumbs.
Shape mixture into golf ball size; place on baking sheet.
When all meatballs are formed, bake for 20 minutes.
While meatballs bake, make sauce.
Preheat small saucepan over medium heat.
Add butter, stir until melted.
Add onion, stirring occasionally, until tender, about 5 minutes.
Sprinkle flour over onion, stir frequently for 2 minutes.
Slowly add apple juice, whisking constantly.
As the sauce starts to thicken, add bourbon, whisking to combine.
When sauce starts to boil, reduce to low, and simmer for 10 minutes.
Season sauce with salt and pepper to taste.
After removing meatballs from oven, allow to cool for 5 minutes, then transfer to saucepan.
Simmer meatballs in sauce for an hour or more.
If desired, serve meatballs with a few apple cubes on top for color and crunch.