French Onion Meatballs

Divide the mixture up into 16 roughly 1 1/2-inch balls. A foolproof way to do this is by forming the meat mixture into an even mound, dividing the mound into quarters, and dividing each quarter into quarters again.

Cook the meatballs:

Heat 2 tablespoons of olive oil in the reserved skillet over medium-high heat. Add the meatballs, making sure to space them evenly, and cook until browned on all sides, 10 to 12 minutes.

Sprinkle flour over the meatballs and toss gently until the flour is cooked, about 1 minute. Add the chicken broth, remaining reserved onions, mustard, and Worcestershire. Stir well, and let simmer until the sauce has thickened and grown slightly darker in color, about 10 minutes.

Add the cheese and broil:

Preheat the broiler on low. Sprinkle the Gruyere over the meatballs and sauce and broil until the cheese is melted, about 2 minutes.

Serve with toasted baguette slices. Leftover meatballs and sauce will keep for up to 5 days in the fridge.