First Step: Prepare and Preheat. Start by preheating your oven to 350°F (175°C). Chop 1 small onion and mince 2 to 4 cloves of fresh garlic. Having your aromatics ready will help you cook the meat sauce quickly and evenly.

Second Step: Cook the Meat and Aromatics. Heat olive oil in a large skillet over medium heat. Add 1/2 pound ground beef and 1/2 to 1 1/2 pounds of ground Italian sausage (casing removed). Cook, breaking the meat apart with a spatula, until browned and no longer pink about 7-10 minutes. Season with salt and pepper. Drain excess fat to avoid greasiness. Add the chopped onions and minced garlic, cooking until onions are translucent and fragrant, about 3-5 minutes. Stir in half of the marinara sauce (12 ounces) and cook for an additional 2 minutes. Remove from heat.

Third Step: Cook the Spaghetti Noodles. Bring a large pot of salted water to a boil. Add 16 ounces dried spaghetti noodles and cook according to package directions until al dente, usually 8-10 minutes. Drain well. Immediately toss noodles with 3 tablespoons butter and the remaining 12 ounces of marinara sauce, coating strands thoroughly for added flavor and moisture. Reserve about 1/2 cup sauce if you prefer to toss noodles separately for better integration.

Fourth Step: Prepare the Cheese Mixture. In a mixing bowl, combine 8 ounces softened cream cheese, 1/4 cup sour cream, and 1 cup cottage cheese or ricotta. Mix until smooth. Add 1 cup shredded mozzarella cheese and the dried Italian seasoning if you’re using it. Stir to create a creamy, herb-infused cheese blend that will layer beautifully in the casserole.

Fifth Step: Assemble the Casserole. Lightly grease a 9×13 inch baking dish. Optionally, lay half the butter slices on the bottom to keep the casserole moist. Spread half of the spaghetti noodles evenly on the bottom. Dollop and spread the cheese mixture evenly over the noodles. Place the remaining noodles over the cheese layer. Pour the meat sauce mixture evenly over the top layer of noodles. Sprinkle the remaining mozzarella cheese (about 1 to 2 cups) and 2/3 cup grated Parmesan cheese over the top.

Sixth Step: Bake Until Bubbly. Bake uncovered in the preheated oven for 30 to 45 minutes. The casserole is done when bubbling around the edges and the cheese is golden brown. Watch carefully if the cheese browns too fast, loosely tent the dish with foil to prevent burning.

Final Step: Rest and Serve. Remove from the oven and let the million dollar spaghetti rest for 10 to 15 minutes before slicing. This helps the layers set for neat servings. Garnish with fresh herbs like basil or parsley if desired. Enjoy a hearty, comforting, and flavorful meal perfect for family dinners or casual entertaining.