Preheat oven to 375 degrees F.
In a deep oven-proof 10-inch skillet, cook the ground beef and sausage over medium high heat. Drain the extra fat. Transfer the cooked meat to a plate, and set aside.
On the same skillet over medium high heat, heat a few drizzles of olive oil and add the diced onions and minced garlic. Cook until fragrant, about 1-2 minutes. Return the cooked meat to the skillet. Add the marinara sauce and Italian seasoning, and stir everything together. Season with salt and pepper to taste. Bring to a low simmer, uncovered, and simmer for 10 minutes, stirring occasionally.
Meanwhile, in a medium bowl, combine the ricotta with the egg, basil, ¼ cup of the parmesan cheese, ½ teaspoon salt, and ¼ teaspoon of ground black pepper. Set aside.
Leave only about 1 cup of the meat sauce in the pan, and transfer the rest of the meat sauce to another bowl.
Build the layers: Add a layer of lasagna sheets on top of the sauce that remains in the skillet (you may have to break up a few lasagna sheets to cover the edges). Then, on top of the lasagna sheets, spread some of the ricotta mixture, some of the meat sauce, and some mozzarella cheese. Repeat this process to get 3 to 4 layers. The last layer should be meat sauce and the mozzarella on top. Sprinkle the remaining ¼ cup of parmesan cheese. The quantities per layer don’t need to be exact, just try to make each layer relatively even.
Cover loosely with aluminum foil. Bake at 375 degrees F for 25 minutes. Uncover and bake for 10-12 more minutes until bubbly. Broil for 1-2 minutes or until golden brown on top.
Garnish with chopped basil. Serve immediately. Enjoy!