Cook Pasta & Cauliflower: In a large pot, cook the pasta according to package directions until al dente.
Make the Sauce: In a saucepan, heat the olive oil over medium heat and sauté the minced garlic for about 1 minute. Stir in the flour to form a light roux. Allow the mixture to simmer for 3–5 minutes until it thickens. Stir in the mustard powder, and season with salt and pepper.
Melt the Cheeses: Lower the heat and stir in 3/4 of the the shredded cheddar and grated mozzarella until the cheese melts completely and the sauce becomes smooth.
Combine & Serve: Mix the cooked pasta into the sauce until evenly coated. For a baked version, transfer the mixture to a greased baking dish, sprinkle with optional whole wheat breadcrumbs and extra toppings, and bake at 375°F (190°C) for 10–15 minutes until the top is lightly golden. Serve warm.