First, slice leeks into disks and leave to soak in cold water for 15 minutes, to remove any soil from between the layers.
Put pasta on to cook (I used shells, conchiglie, for this). Cut up some leftover cooked ham into chunks and place in a casserole dish.
Sauté the leeks in a little butter until softened and add these to the ham. Make a cheese sauce by melting butter in a saucepan,
adding a Tbs plain flour and cooking the roux for a few minutes, before adding whole milk, stirring all the while until you have
a nice thick smooth sauce. Add a good handful of grated sharp cheddar cheese, stirring until melted. When the pasta is cooked,
drain and add to the ham and leeks. Stir the cheese sauce into the pasta mixture, and sprinkle over a mixture of panko breadcrumbs
and freshly grated parmesan cheese. Bake in a 180°C oven for 30 minutes, until bubbling and crisp and golden on top.
Serve with a mixed salad.