1-First Step: Prep the oven and pasta water Arrange one rack in the top position and another in the middle of the oven, then heat the oven to 375°F. Put a large pot of water on the stove and season it generously with salt. Once it comes to a boil, cook the spaghetti 1 minute less than the package directions for al dente.

2-Second Step: Make the roux While the pasta water heats, melt 3 tablespoons unsalted butter in a medium pot over medium heat. Whisk in 3 tablespoons all-purpose flour and keep stirring for about 2 minutes, until the mixture turns golden brown. This is the start of the sauce, and it gives the Alfredo base body and flavor.

3-Third Step: Whisk in the milk and cream Slowly whisk in 3 cups whole or 2 percent milk and 1 cup heavy cream. Add the liquid little by little so the sauce stays smooth. Bring it to a boil, then reduce the heat and simmer for about 5 minutes, or until it thickens slightly.

4-Fourth Step: Add the cheese and seasonings Take the pot off the heat. Whisk in 4 ounces of the shredded mozzarella, 3 ounces of the Parmesan, 1/2 teaspoon garlic powder, and 1 teaspoon kosher salt. Stir until the sauce is smooth and glossy.

5-Fifth Step: Combine the pasta and sauce Drain the spaghetti as soon as it reaches that just-under-al-dente stage. Add it straight into the sauce and toss until every strand is coated. Make sure the sauce gets between the noodles so the final bake stays creamy all the way through.

6-Sixth Step: Assemble the baking dish Transfer the pasta mixture to an 8×8, 9×9, or 9×13-inch baking dish. Use a spoon or tongs to spread the noodles out evenly so the top browns in a nice even layer. Sprinkle the remaining 2 ounces of mozzarella and 1 ounce of Parmesan over the top.

7-Seventh Step: Bake and broil Bake on the middle rack for about 20 minutes, until the edges are bubbling and the cheese is melted. Then move the dish to the top rack and broil for 3 to 4 minutes, just until the top is browned. Watch it closely during broiling because cheese can go from golden to too dark very quickly.

8-Final Step: Finish and serve Garnish with finely chopped fresh parsley leaves if you want a little color and freshness. Serve warm and creamy straight from the baking dish. This recipe feeds 6, and it works well with a simple side salad, roasted vegetables, or garlic bread.