PREPARE pasta according to package instructions when water boils. Drain well.
MAKE a roux by melting butter in a medium saucepan over medium heat while pasta cooks. Sprinkle flour over the melted butter and stir to dissolve flour into the butter. Cook flour in butter for 1 - 2 minutes. Whisk in milk and continue whisking until all of the flour is incorporated into the milk. Scrape along edges of the saucepan with a heat-proof spatula make sure no roux remains in the corners.
WHISK in Dijon mustard, garlic powder, ¼ teaspoon salt and pepper. Whisking constantly, increase heat to medium-high and bring to a simmer and cook until thickened, 2 to 3 minutes.
REMOVE the thickened sauce from the heat. Stir in shredded Gouda & cheddar cheese and whisk until completely melted into the sauce.
STIR the hot cooked pasta and sauce together in the pasta pot. Serve hot.
Ingredients
Salt for pasta water plus ¼ teaspoon, divided
16 ounces dry pasta, such as fusilli, rotini or macaroni, whole-wheat if desired
