Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish.

In a large skillet over medium heat, combine the ground beef and ground mild Italian sausage. Cook until browned, breaking up the meat with a spoon as it cooks. Drain excess fat.

Add the chopped onion and minced garlic to the skillet. Cook until the onion is translucent and fragrant, about 3-5 minutes.

Season with salt, pepper, and Italian seasoning. Stir in the marinara sauce and let it simmer on low heat while you prepare the cheese mixture.

In a medium mixing bowl, combine the softened cream cheese, sour cream, and ricotta cheese. Mix until smooth and well blended.

In the prepared baking dish, start with a layer of half the cooked spaghetti. Spread the cheese mixture evenly over the spaghetti layer. Add the remaining spaghetti on top of the cheese mixture. Pour the meat sauce evenly over the top layer of spaghetti.

Sprinkle the grated Parmesan cheese and shredded mozzarella cheese evenly over the top of the meat sauce.

Cover the baking dish with aluminum foil and bake in the preheated oven for 30 minutes. Then, remove the foil and bake for an additional 10-15 minutes, or until the cheese is melted and bubbly.

Remove from the oven and let it cool for a few minutes before serving. Enjoy!