In a large skillet, heat the olive oil over medium heat. Add the Italian sausage, breaking it up with a spoon, and cook until browned, about 5-7 minutes.

Add the chopped onion and cook until softened, about 3-4 minutes. Add the minced garlic and cook for 1 minute more, until fragrant.

Pour in the premade marinara or tomato sauce. Stir well and let the sauce simmer for 5-10 minutes. Season with salt and pepper to taste, then remove from heat and set aside.

In a mixing bowl, combine the ricotta cheese, mascarpone cheese, egg, grated Parmesan, salt, and pepper. Mix until smooth and creamy.

Preheat the oven to 375°F (190°C).

In a 9x13-inch baking dish, spread a thin layer of the meat sauce on the bottom.

Place 3 cooked lasagna noodles on top of the sauce.

Spread 1/3 of the ricotta-mascarpone mixture over the noodles, then sprinkle 1 cup of shredded mozzarella cheese on top.

Spoon another layer of meat sauce over the cheese layer.

Repeat the layers two more times: noodles, ricotta mixture, shredded mozzarella, and meat sauce.

Finish with Mozzarella:

For the top layer, add the remaining meat sauce and sprinkle the final cup of shredded mozzarella cheese evenly over the top.

Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes.

Remove the foil and bake for an additional 15-20 minutes, or until the cheese on top is melted and bubbly and the lasagna is heated through.

Let the lasagna cool for 10-15 minutes before slicing to serve. This helps it hold its shape.