Preheat oven to 400℉ (200℃) and grease or line a baking sheet.
In a large mixing bowl, combine all the meatball ingredients. Use hands or large spoon to mash and mix thoroughly.
Use about 1 ½ tablespoon of the meat mixture to roll and form about 20 round ball shapes. Place each meatball on the prepared baking sheet.
Bake for 15 to 20 minutes or until meatballs is browning and done in the center.
While meatballs are baking, heat a large frying pan over medium-high heat on the stovetop.
Add butter to the frying pan and melt. Add minced garlic and saute until fragrant.
Add chopped mushrooms, tamari sauce or coconut aminos and saute until mushrooms are browned and softened.
Add beef broth, heavy cream, dijon mustard, and stir until combined. Bring sauce in the pan to bubbling then lower heat to medium. Stir occasionally and lower temperature to simmer for 5 to 6 minutes to thicken.
Add salt and pepper, optional cayenne pepper and stir. Sprinkle with optional xanthan gum and whisk if more thickening is desired.
Remove meatballs from the oven when done. Add meatballs to the frying pan with the sauce and coat in sauce. Serve as is or over cauliflower mash.
*all nutritional data are estimates based on the products I used*