Preheat your oven to 180°C (160°C fan) and lightly grease a large 9x13 inch baking dish.

Cook the macaroni in a large pot of well-salted boiling water according to package directions, but undercook it by 2 minutes. This is important as it will continue to cook in the oven. Drain well and set aside.

While the pasta cooks, start the sauce. In a large, heavy-bottomed saucepan or Dutch oven, melt the 80g of butter over a medium-low heat. Once melted, whisk in the plain flour and cook, stirring constantly, for 2 minutes. This is your roux, and cooking it out prevents a raw flour taste.

Gradually pour in the warm milk, about 100ml at a time, whisking continuously to prevent any lumps from forming. Once all the milk is incorporated, increase the heat to medium and bring the sauce to a gentle simmer, stirring often. Cook for 5-7 minutes, until the sauce has thickened enough to coat the back of a spoon. For a full guide on this technique, BBC Good Food has a great tutorial on making a perfect Béchamel.

Crucial step: Remove the saucepan from the heat. This prevents the cheese from becoming oily or grainy. Add the Dijon mustard, nutmeg, smoked paprika, and most of the grated cheddar and Gruyère (reserve a small handful of each for the topping). Stir gently until the cheeses are completely melted and the sauce is smooth and velvety. Season generously with salt and pepper to your taste.

Pour the cooked macaroni into the cheese sauce and stir until every piece of pasta is well coated. What works best for me is using a large spatula to gently fold everything together.

In a small bowl, combine the panko breadcrumbs, melted butter, grated Parmesan, the reserved cheddar and Gruyère, and the pinch of paprika. Mix until the breadcrumbs are evenly coated.

Pour the macaroni and cheese mixture into your prepared baking dish and spread it into an even layer. Sprinkle the breadcrumb topping evenly over the surface.

Bake for 25-30 minutes, or until the top is golden brown and the sauce is bubbling around the edges. Let it rest for 5-10 minutes before serving. This allows the sauce to set up slightly.