In a small skillet over medium heat, add the butter and the onion. Cook the onion until softened, 5-10 minutes. Add in the all spice and garlic and cook for 1 minute more. Remove from the heat and set aside.
In a large bowl add the ground beef, milk, egg, pork rinds, 1 teaspoon of Worcestershire, onion mixture, salt and pepper. Mix well and form into meatballs. Add meatballs to the crockpot and pour over beef broth.
Cook on low for 8 hours or high for 4 hours. When the time is finished, remove the meatballs from the crockpot and set aside.
Add the heavy cream, remaining Worcestershire, and xanthan gum to the liquid in the crockpot. Stir well to combine and let thicken. Add the meatballs back to the crock pot and stir. Serve