Combine the beef, almond flour, egg, onion, Worcestershire sauce, garlic powder, salt, and pepper. Shape into 16 meatballs.
Heat olive oil in a skillet and brown the meatballs on all sides. Remove and set aside.
Add butter to the skillet and cook the mushrooms until softened and browned.
Stir in Dijon mustard and Worcestershire sauce.
Pour in beef broth, scraping the pan.
Add heavy cream, salt, and pepper.
Return the meatballs to the skillet and simmer 10–12 minutes, until the gravy thickens.
Serve warm.