Add ground beef, breadcrumbs, grated onion, minced garlic, and salt & pepper (to taste) to a mixing bowl and gently mix together, using your hands.
Form meatballs (should make about 35 1-inch meatballs).
Dredge meatballs in flour.
On medium heat, melt olive oil and about 1 tbsp of butter in pot. Add meatballs and brown for a couple of minutes per side.
Once meatballs are browned, remove and set aside on a separate plate.
Deglaze the pan with the wine and dijon mustard.
Add cream, chicken broth, worcestershire sauce, the rest of the butter, nutmeg, 2 teaspoons of flour (sprinkle in gradually while stirring), and more pepper to sauce. Increase heat to medium-high, and stir until sauce is smooth. Reduce heat to medium just as sauce comes to a boil.
Add meatballs into pot and cook for approximately 20 minutes on medium-low heat until meatballs are cooked through and sauce is thickened. Stir them occasionally.
Add extra salt and pepper if desired.