2 tablespoons olive oil
1 1/2 lbs ground beef
1/2 cup breadcrumbs
2 tablespoons Dijon mustard
3 tablespoons ketchup
2 tablespoons Worcestershire sauce, divided
1 large white onion, thinly sliced
1/4 cup (1/2 stick) unsalted butter
2 cloves garlic, minced
1/4 cup all-purpose flour
2 cups beef stock
Kosher salt and freshly ground black pepper, to taste
In a large bowl, mix together ground beef, breadcrumbs, egg, mustard, ketchup, and 1 tablespoon Worcestershire sauce. Season with salt and pepper, mix again, and roll into 1 1/2-inch balls.
Heat olive oil in a large skillet over medium-high heat. Working in batches, brown meatballs on both sides. Remove to a plate and set aside.
Reduce skillet to medium heat. Add onions and cook until soft and lightly browned, 5-10 minutes.
Add butter to skillet. Once melted, stir in garlic and cook until fragrant, 1 minute more.
Whisk in flour and cook another minute. Slowly pour in beef broth and cook until bubbly and thickened.
Stir in remaining Worcestershire sauce and season with salt and pepper.
Return meatballs to pan and simmer until cooked through, 3-4 minutes.
Serve over egg noodles or mashed potatoes and enjoy!