You will need:
Heat the oven to 200°C/Gas 6. Boil the macaroni in a pan of salted water until nearly cooked, about 8 minutes. It should be slightly too al dente to eat. Drain and toss in a little olive oil to stop it sticking together. While the pasta is cooking, melt the butter in a small pan on a low heat. Add the leeks and cook gently until soft, about 7 minutes, stirring now and then. Add the flour and stir over a low heat for 2 minutes, then gradually stir in the milk (a whisk helps avoid lumps). Add the cheese and heat gently, stirring, to thicken the sauce and melt the cheese. Season to taste with mustard, salt and pepper. Combine the pasta with the leek mixture and transfer to a baking dish. Sprinkle over a little more cheese and the breadcrumbs, if using, and bake for about 20 minutes, until golden on top. Variation * Add some leftover cooked chicken or fried bacon pieces to the leek mixture before baking. * For extra veg, stir through some blanched and chopped kale, cabbage, spinach, chard or broccoli. www.riverford.co.uk/recipes