Cook the macaroni according to package instructions. Drain and set aside.

In a large pot, melt butter over medium heat. Add finely chopped onion and diced courgette. Sauté until vegetables are softened.

Stir in plain flour and cook for 2 minutes to create a roux.

Gradually whisk in the milk to avoid lumps. Continue to stir until the mixture thickens.

Add mustard, cayenne pepper, shredded cheddar, and grated parmesan to the sauce. Stir until the cheeses are melted and the sauce is smooth.

Season with salt and pepper to taste. If the sauce is too thick, you can add more milk to reach your desired consistency.

Add the cooked macaroni to the cheese sauce, tossing until the pasta is well coated.

Preheat the oven to 200°C (400°F).

Transfer the mac and cheese to a baking dish. In a small bowl, mix breadcrumbs with garlic powder. Sprinkle the breadcrumb mixture over the macaroni.

Bake in the preheated oven for 15-20 minutes or until the top is golden brown and the cheese is bubbly.

Remove from the oven, let it cool for a few minutes, and then serve your homemade mac and cheese hot. Enjoy the cheesy goodness!