People’s appetites vary so much that it’s hard to give exact serving amounts, especially when duck legs are on the menu. If you’re serving just breasts, a whole breast from a Long Island duckling (Pekin duck) is just right for a single main-course serving. If you’re serving mullard breasts, half a breast per person is about right. If you’re serving the legs, one leg alone can serve one, but it’s a bit of a stretch, especially if your guests are big eaters and you haven’t served a first course. Two legs, on the other hand, is usually too much. I sometimes resolve this problem by dividing the legs into thighs and drumsticks and giving everyone two of one and one of the other. You can also serve duck legs and breasts together: Serve half a sliced mullard breast with a whole duck leg; or serve most or all of a Pekin duck breast with a duck leg to produce a generous main-course serving.