Preheat the oven to 350°F (175°C).

Cook the spaghetti according to package instructions; drain and set aside.

In a large skillet, heat olive oil over medium heat. Add the ground beef and cook until browned. Add the onion and garlic, cooking until the onion is soft.

Stir in the marinara sauce, salt, and pepper. Simmer for 5 minutes.

In a bowl, combine the softened cream cheese, sour cream, and Parmesan cheese until smooth.

Toss the cooked spaghetti with the cheese mixture until coated.

Spread a thin layer of the meat sauce in a baking dish. Add the spaghetti mixture, then top with remaining meat sauce.

Sprinkle mozzarella cheese over the top.

Bake in preheated oven for 25-30 minutes until cheese is melted and bubbly.

Garnish with fresh parsley before serving.