Heat a large skillet over medium-high heat. Add the ground beef and cook, breaking it into crumbles, until browned. Drain excess fat if necessary.

Reduce the heat to medium and add the Italian sausage. Cook until mostly browned.

Add the onion and bell pepper and cook until the meats are completely cooked and the vegetables have softened.

Add the minced garlic and cook for approximately 1 minute, until fragrant.

Season with salt and black pepper to taste. Add the pasta sauce and stir well.

Reduce the heat to low and simmer the meat sauce for approximately 30–45 minutes.

Meanwhile, cook the spaghetti in a large pot of salted boiling water until al dente. Drain well.

In a medium bowl, combine the sour cream, cottage cheese, softened cream cheese, Parmesan, and a portion of the chopped green onions. Season with salt and black pepper to taste.

Preheat the oven to 375°F.

Spread a layer of meat sauce over the bottom of a 9x13-inch casserole dish and sprinkle with additional Parmesan if desired.

Spread the cooked spaghetti evenly over the sauce.

Spread the creamy cheese mixture evenly over the spaghetti.

Spoon the remaining meat sauce over the creamy layer.

Cover evenly with shredded mozzarella and sprinkle with dried parsley.

Bake at 375°F for approximately 30–45 minutes, until hot and bubbly and the cheese is completely melted.

Add the remaining green onions during the final 15 minutes of baking, if desired.

For an extra golden top, broil for approximately 2–3 minutes, watching carefully.

Allow the casserole to rest for 10–15 minutes before serving.