Preheat the oven to 200C/400F/Gas 6. Cook the macaroni in plenty of boiling salted water for 8-10
minutes, until tender. Drain well. Melt the butter in a saucepan, add the leeks and cook, stirring
occasionally, for about 4 minutes. Stir in the flour, cook for 1 minute, then remove the pan from
the heat. Gradually stir the milk into the pan, then return to the heat
and bring to the boil, stirring. Simmer for about 3 minutes.
Remove from the heat and stir in the macaroni and most of the
cheese, and season to taste. Pour the macaroni mixture into a baking dish. Mix together the breadcrumbs and the remaining cheese, then
sprinkle over the dish. Bake for 20-25 minutes, until the topping is golden.
Leeks add a new twist and extra flavor to an ever popular family
favorite. The sauce can be flavored with mustard or chopped herbs, such as
parsley, chives or thyme.