Mary Berry says: “This is the perfect supper dish, which I like to serve with crusty French bread. You can vary the cheese: for example, if you have leftover pieces of Camembert or Brie, freeze them with the skin on, grate when frozen, and add the cheese to the sauce.”
1 Preheat the oven to 200°C (fan 180°C/400°F/Gas 6). Lightly grease a medium, shallow baking dish. Cook the macaroni in a pan of boiling salted water for about 10 minutes (or according to packet instructions) until just tender, stirring occasionally. Drain well and set aside.
2 While the macaroni is cooking, melt the butter in a large pan. Sprinkle in the flour and cook, stirring, for 1–2 minutes. Remove the pan from the heat and gradually stir in the milk. Return to the heat, bring to the boil, stirring constantly until the mixture thickens. Lower the heat and simmer for about 4–5 minutes, stirring often, until the sauce is thick and smooth.
3 Remove the sauce from the heat. Mix the two cheeses together. Stir the mustard into the sauce with most of the cheese (reserve a handful for the topping) and the macaroni, then season with salt and pepper.
4 Spoon the macaroni cheese into the baking dish, then scatter over the halved cherry tomatoes and the reserved cheese. Season with pepper. Bake for about 15–20 minutes until golden and bubbling. For a browner topping, finish off quickly under a hot grill. Garnish with parsley.