Cheesy Spaghetti Casserole Delight: A Cozy Family Favorite

Bring a large pot of salted water to a rolling boil. Add the spaghetti and cook until just shy of al dente—about 8‑9 minutes. Drain, reserving ½ cup of pasta water, then set the noodles aside. This brief under‑cooking ensures the pasta finishes perfectly in the oven without becoming mushy.

Building the Cheese Sauce

1. Make a roux. In a medium saucepan over medium heat, melt 2 tablespoons unsalted butter. Sprinkle 2 tablespoons all‑purpose flour over the butter, whisking constantly for 2 minutes until the mixture turns a light golden hue. This cooking step eliminates raw flour flavor.
2. Incorporate milk. Slowly pour the warmed 2 cups whole milk into the roux while whisking. Continue to stir until the sauce thickens and coats the back of a spoon, about 4‑5 minutes. If the sauce seems too thick, add a splash of the reserved pasta water.
3. Blend cheeses and marinara. Reduce heat to low, then stir in 1 ½ cups marinara sauce, 1 ½ cups shredded mozzarella, 1 cup shredded cheddar, and ½ cup grated Parmesan. Mix until the cheeses melt into a glossy, uniform sauce. Season with 1 teaspoon dried oregano, ½ teaspoon garlic powder, ¼ teaspoon red pepper flakes (if using), salt, and pepper.
4. Combine pasta and sauce. Toss the cooked spaghetti into the cheese sauce, ensuring every strand is evenly coated. The residual heat from the pasta helps the sauce cling, creating a cohesive mixture ready for baking.