Cook the Spaghetti. Begin by bringing a large pot of salted water to a boil. Add your spaghetti and cook according to the package instructions until al dente, usually about 8-10 minutes. Once done, drain the spaghetti in a colander and set it aside to cool slightly while you prepare the creamy sauce.

Prepare the Cream Cheese Sauce. In a mixing bowl, combine the softened cream cheese, marinara sauce, garlic powder, Italian seasoning, salt, and pepper. Use a spatula or mixer to blend the ingredients until smooth and creamy, which should take about 2-3 minutes. If you prefer a richer texture, feel free to fold in some sour cream at this stage.

Combine Pasta and Sauce. Add the drained spaghetti to the bowl with the cream cheese sauce. Gently toss the noodles with the sauce until every strand is generously coated. Aim for a uniform mixture, ensuring the creamy sauce envelops the spaghetti beautifully, which should take about 1-2 minutes.

Assemble the Casserole. Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish with cooking spray or butter to prevent sticking. Spoon the spaghetti mixture into the prepared dish, spreading it evenly to create a uniform base for your Spaghetti Casserole Heaven.

Top with Cheese. Sprinkle the shredded mozzarella, cheddar, and grated Parmesan evenly over the spaghetti mixture. Make sure all areas are covered to achieve that deliciously cheesy crust. This should take about 1 minute, but ensure that the topping is generous for maximum meltiness.

Bake to Perfection. Place the assembled casserole in the preheated oven and bake for 25-30 minutes. Keep an eye on it; you’re looking for the cheese to be wonderfully melted, bubbling, and turning golden brown on top, indicating that it’s ready to enjoy.

Garnish and Serve. Once baked, remove the casserole from the oven and let it cool for about 5-10 minutes. This brief resting period helps firm up the dish. If desired, garnish with fresh basil or parsley for a pop of color before serving your delicious Spaghetti Casserole Heaven to family and friends.