Method

1. Preheat the oven to 200C/180C Fan/Gas 6. Bring a large pan of salted water to the boil and add the macaroni. Cook for 5 minutes then drain.

2. Meanwhile trim the leeks, discarding the green parts, then thinly slice. Melt the butter in a large saucepan, add the leeks and cook gently for 5 minutes, or until soft. Add the flour and cook for 2 minutes, stirring constantly. Add the milk little by little, stirring constantly, then cook gently for 5 minutes, stirring all the time until the sauce is thickened. Add the mustard and Worcestershire sauce then remove from the heat. Stir in the grated cheese and season with salt and pepper.

3. Add the pasta to the sauce, stir to combine then pour into a 2 litre/3½ pint ovenproof dish. Sprinkle over the breadcrumbs and bake for 25 minutes until golden-brown.

4. Towards the end of cooking, bring a pot of water to the boil. Add the peas, cook for 3-4 minutes then drain. Serve the macaroni cheese with the peas.