• Make meatballs: In a large bowl, combine the 1 pound ground beef, egg, 1/4 cup breadcrumbs, 1/4 cup chopped onion, 2 teaspoons garlic, 3/4 teaspoon salt, and 1/4 teaspoon pepper.
• Form meatballs: Heat 1 - 2 Tablespoons olive oil in a large skillet over medium heat. Use a medium cookie scoop or spoon to scoop the meat mixture. Form into 1 1/2-inch balls and place on the hot skillet. 
• Cook: Fry meatballs for 7 - 10 minutes, or until cooked through. Flip every few minutes to prevent burning. Remove the meatballs from the pan and set aside on a plate lined with paper towels.

Sauce

• Sauté: In the same skillet, over medium high heat, add the sliced onions and sauté for 5 minutes. Add 2 teaspoons minced garlic and cook another 30 seconds.
• Cook sauce: In a small bowl or cup, whisk together 2 cups beef broth and 1 1/2 teaspoons cornstarch until it's smooth. Pour in the skillet with the onions. Use a wooden spoon to stir and scrape the browned bits from the bottom of the pan. Stirring continuously, cook on high for 4-5 minutes, until thickened.
• Add meatballs: Return the cooked meatballs to the skillet, spooning the sauce over the meatballs.
• Let rest: Let the meatballs and sauce rest, uncovered, for 5 minutes so the sauce will thicken just a little more and the meatballs will heat back up.

Bread Topping

• Preheat and prepare: Meanwhile, preheat the oven to 450°F and line a baking sheet with parchment paper or foil.
• Cook bread: Lightly brush both sides of baguette slices with olive oil and toast in the oven for 4 minutes until lightly browned. Add shredded cheese on each piece of bread and cook another 2 minutes.
• Serve: Place two pieces of toasted bread on each dish of before serving.