Cook the pasta:
In a large pot, bring salted water to a boil. Add macaroni and cook until al dente (about 7–8 minutes). Drain and set aside.

Make the cheese sauce:
In a saucepan, melt butter over medium heat. Stir in the flour and cook for 1–2 minutes, whisking constantly to form a smooth roux.
Slowly whisk in the milk, continuing to stir until the sauce thickens, about 4–5 minutes.

Add the cheese:
Reduce the heat and stir in the cheddar, mozzarella, mustard powder (if using), salt, and pepper. Stir until smooth and creamy.

Combine pasta and sauce:
Add the drained macaroni to the cheese sauce and stir until evenly coated.

Optional bake with topping:
Preheat oven to 180°C (350°F). Transfer the mac and cheese to a greased baking dish. Mix breadcrumbs with melted butter and sprinkle over the top. Bake for 15–20 minutes until golden and bubbly.

Serve:
Serve hot, straight from the pot or baked dish. Delicious with a fresh green salad or crispy bacon bits on top!

‍