Cut the unpeeled apples into pieces, put into a pan with 2 oz (50 g) of the butter and cook very gently until the apples are soft. Put through a sieve. Meanwhile, boil the potatoes. Drain and purée, then stir into the cooked apples. Warm the milk and stir in and add 1 oz (25 g) of the butter.
Turn the breadcrumbs round in a pan with the remaining 1 oz (25 g) of butter until they are crisp. Strew over the purée and serve.