Christophene au Gratin

• 5 large chayotes, each weighing about ¾ lb.
• 2½ oz. unsalted butter

Boil the whole chayotes in salted water until tender, about 30 minutes. Remove from the saucepan, and when cool enough to handle, cut into halves lengthwise. Scoop out the pulp, including the edible seed, mash and set aside. Reserve the shells.

Heat 1½ oz. of the butter in a frying pan and sauté the onion until tender but not browned. Add the mashed chayote pulp, salt and pepper to tast