Stuffed Shells with Meat and Cheese features jumbo pasta shells with ricotta, ground beef, mozzarella, and Parmesan, topped with marinara and baked until bubbly!
Preheat the oven to 400° and have ready a greased 9x13" casserole dish.
Cook ½ of a 12-ounce package of shells (about 20 shells) to al dente according to package directions, drain, and set aside to cool.
While waiting on the shells to cook, begin on the filling. Add the olive oil to a large sauté pan over medium-high heat and allow to come to temperature. Add the onion and sauté 3-4 minutes, just until softened.
Add the beef, break it apart with a wooden spoon, and season with 1 teaspoon garlic powder, 1 teaspoon Kosher salt, and ¾ teaspoon black pepper. Cook for 6-8 minutes, until the beef is fully cooked through.
Remove the beef from the pan using a slotted spoon and add to a large mixing bowl along with ricotta, 1 cup mozzarella, Parmesan, egg, egg yolks, and 2 tablespoons chopped basil (if using). Stir to combine well and set aside.
In a medium-sized mixing bowl, add tomato sauce, sugar, 2 teaspoons garlic powder, 1 teaspoon Kosher salt, 1 teaspoon pepper, and 1 tablespoon chopped basil (if using). Stir and set aside.
Add about ¾ cup of the marinara sauce to the bottom of the casserole dish. Fill each shell with about 2 tablespoons of the beef filling (a cookie scoop works great for this task) and place them seam-side up in the casserole dish. Once your shells are filled, pour the remaining sauce across the tops of them, and sprinkle with the remaining cup of mozzarella cheese.
Cover the dish with foil, and bake for 20 minutes. Remove the foil and continue to bake until the edges are hot and bubbly, about 5 minutes more. Serve and enjoy.