Preheat and prepare: Set your oven to 180°C (350°F). Grease a 9x13 inch baking dish with a little butter. Bring a large pot of salted water to a rolling boil.

Cook the pasta: Add the macaroni and cook for 1-2 minutes less than the packet suggests. It should be al dente — firm to the bite. The pasta will finish cooking in the oven. Drain it in a colander and set aside. You’ll hear a slight hiss as the steam escapes.

Make the roux: In a large saucepan, melt the 115g of butter over a medium heat. Once it has fully melted and begins to foam gently, whisk in the flour. Cook for 2 minutes, stirring constantly, until the mixture turns a pale, biscuit-like colour and smells nutty.

Build the sauce: Slowly pour in the milk and double cream in a steady stream, whisking vigorously to prevent lumps. The sauce will thicken after about 5-7 minutes. You’ll know it’s ready when it coats the back of a spoon and you can draw a clean line through it with your finger.

Season and melt the cheese: Reduce the heat to low. Stir in the salt, pepper, paprika, cayenne (if using), and mustard powder. Add the grated cheddar and Gruyère, reserving a large handful for the topping. Stir until the cheeses are fully melted and the sauce is smooth and glossy. Taste it — the warmth from the paprika should just hum on your tongue.

Combine and assemble: Tip the drained pasta into the cheese sauce. Stir gently but thoroughly until every piece of macaroni is coated. Pour the mixture into your prepared baking dish and spread it into an even layer.

Top and bake: Sprinkle the reserved cheddar and Gruyère over the top, followed by the grated Parmesan. For an extra-crunchy crust, dot with a few small cubes of butter. Bake uncovered for 25-30 minutes, until the top is a deep golden brown and the sauce is bubbling around the edges. You’ll hear a gentle, steady bubbling sound as it bakes.

Rest and serve: Remove the dish from the oven and let it rest for a full 10 minutes. This is crucial — it allows the sauce to set slightly so it doesn’t run across the plate. The surface will be crackling and fragrant.