Sift together the flour, baking powder, and salt. Combine the breadcrumbs, sugar, suet, and cranberries with the milk. Add the flour mixture. Pour into a greased mold, filling it only 2/3 full. Cover tightly. Place the mold on a rack in a kettle over 1 inch of boiling water and steam for 2 hours, using high heat at the beginning and, as the steam escapes, lowering the heat. Add water if necessary. Serve with hard sauce.