Beef Casserole Belgian Style

750 g topside or silverside of beef, cut into 2.5 cm cubes
60 g butter
40 cl beef stock
175 g dried apricots
1 teaspoon sugar
4 or 5 leeks, white parts only
Salt and pepper
1 teaspoon grated lemon rind

Brown the beef briskly in butter in a casserole set over fairly high heat. Add the stock, apricots, and sugar, reduce the heat to low and leave to simmer. Blanch the leeks by putting them into cold water and gradually bringing them to the boil; then drain them. Add the leeks to the casserole and season to taste. Cover and simmer gently for 2 hours. Check the seasoning, add the lemon rind, stir and then simmer for 5 minutes more. Serve with mashed potatoes and flageolets or Lima beans.