Boil the leeks for 5-10 minutes, strain and combine with the mashed potato. Season well and beat in half the butter until the mixture is fluffy. Arrange on a greased ovenproof dish.

To make the cheese sauce, melt 25g (1 oz) of butter in a saucepan and stir in the flour. Cook for 2 minutes, stirring constantly. Remove from the heat and gradually add the hot milk, mixing vigorously. When smooth, return to the heat and bring to the boil, stirring all the while. Allow to simmer gently until thick. Add nutmeg, most of the grated cheese and season to taste.

Halve the hard-boiled eggs and arrange on the bed of leek and potatoes. Cover with the cheese sauce, sprinkle with the remaining grated cheese and dot with the remaining butter. Bake at 200 �C / 400 �F / Gas 6 until brown.