Mix the aromatics. In a bowl, combine minced onion, garlic, almond flour, egg, heavy cream, salt, pepper, allspice, and nutmeg.
Stir until the almond flour absorbs some moisture and the mixture looks like a thick paste.
Combine with the meat. Add ground beef and ground pork. Gently mix with your hands until just combined. Do not overwork or the meatballs will turn dense.
Shape the meatballs. Form into 1 to 1 1/4-inch balls. You should get about 30–36.
Chill them in the fridge for 15 minutes to help them hold their shape.
Brown the meatballs. Heat butter or oil in a large skillet over medium heat. Brown the meatballs in batches, turning to color all sides, about 6–8 minutes total. Transfer to a plate; they’ll finish cooking in the sauce.
Make the gravy base. In the same skillet, lower the heat to medium-low.
Add 2 tbsp butter and let it melt, scraping up browned bits with a spatula for flavor.
Add liquids and season. Pour in the beef broth, heavy cream, Dijon, and Worcestershire. Whisk to combine and bring to a gentle simmer.
Thicken the sauce. If using xanthan gum, lightly sprinkle it over the surface while whisking constantly. Start with 1/8 tsp, then add up to 1/4 tsp as needed.
Simmer 2–3 minutes until the gravy coats a spoon.
Finish cooking the meatballs. Return meatballs to the skillet. Simmer gently for 8–10 minutes, or until cooked through and the sauce is rich. Taste and adjust salt and pepper.
Garnish and serve. Sprinkle with fresh parsley.
Serve over mashed cauliflower or zoodles, and spoon on extra sauce.