Melt the butter in a large, oven-safe skillet over a medium heat. Add the minced garlic and cook for about 1 minute until fragrant, but not browned.

Whisk in the plain flour, mustard powder, and smoked paprika. Cook for another minute, stirring constantly, to form a paste (this is called a roux). This step cooks out the raw flour taste.

Gradually pour in the whole milk, a little at a time, whisking continuously to avoid lumps. Once all the milk is incorporated, pour in the stock and bring the mixture to a gentle simmer.

Add the dried macaroni to the skillet and stir well to combine. Let it simmer gently over a medium-low heat for 10-12 minutes, or until the pasta is al dente. Stir frequently to prevent the pasta from sticking to the bottom of the pan. What works best for me is a gentle stir every couple of minutes.

While the pasta is cooking, preheat your grill to a medium-high setting.

Once the pasta is cooked and the sauce has thickened beautifully, remove the skillet from the heat. Add about three-quarters of the grated cheddar and all the Gruyère to the pan. Season generously with salt and pepper.

Stir everything together until the cheese is completely melted and the sauce is smooth and glossy. The sauce should coat the back of a spoon.

Sprinkle the remaining cheddar cheese and the fresh breadcrumbs (if using) evenly over the top of the mac and cheese.

Place the skillet under the preheated grill for 3-5 minutes, or until the top is golden brown and bubbling deliciously. Keep a close eye on it to prevent it from burning!

Remove from the grill and let it rest for a few minutes before garnishing with fresh parsley and serving hot.