Prepare the Pasta and Oven: Preheat your oven to 180°C (160°C fan). Bring a large pot of heavily salted water to a rolling boil. Add the pasta and cook according to package directions, but undercook it by about 2 minutes so it is very al dente. It will finish cooking in the oven. Before draining, reserve about 250ml (a mugful) of the starchy pasta water. Drain the pasta and set aside.

Start the Roux: While the pasta is cooking, begin the sauce. In a large, heavy-bottomed saucepan or Dutch oven, melt the butter over a medium-low heat. Once melted, whisk in the plain flour and cook, stirring constantly, for 1-2 minutes. This step cooks out the raw flour taste.

Make the Béchamel Sauce: Gradually pour in the warm milk, a little at a time, whisking continuously to prevent lumps. Once all the milk is incorporated, turn the heat up slightly and bring the sauce to a gentle simmer, stirring often. Let it simmer for 2-3 minutes until it has thickened enough to coat the back of a spoon. For a full tutorial, BBC Good Food has an excellent guide on how to make a perfect béchamel sauce.

Add the Cheeses: Remove the saucepan from the heat completely. This is a crucial step to ensure a smooth sauce. Add the grated Cheddar, mozzarella, 50g of the Parmesan, Dijon mustard, and freshly grated nutmeg. Season with a generous pinch of salt and black pepper. Stir until the cheeses are completely melted and the sauce is smooth and velvety. What works best for me is letting the residual heat do the work.

Combine Pasta and Sauce: Pour the drained pasta into the cheese sauce. Stir everything together until every piece of pasta is thoroughly coated. If the sauce seems a little too thick, add a splash of the reserved pasta water to loosen it to your desired consistency.

Assemble for Baking: Transfer the cheesy pasta mixture to a 2-litre ovenproof baking dish and spread it out in an even layer.

Prepare the Topping: In a small bowl, mix the Panko breadcrumbs with the remaining 2 tablespoons of grated Parmesan and the olive oil. Use your fingertips to toss everything together until the breadcrumbs are lightly coated.

Bake to Perfection: Sprinkle the breadcrumb mixture evenly over the top of the pasta. Place the dish in the preheated oven and bake for 20-25 minutes, or until the sauce is bubbling around the edges and the topping is crisp and a deep golden brown. Let it rest for 5 minutes before serving.