Draw and singe the pair of guinea hens, removing the wings, thighs and legs and leaving the breast whole. Break the back of the carcass and then place in a deep saucepan and add 7 cups of boiling water and steam slowly until tender. Add carrot, onion, and celery for flavoring and then lift and set the thighs and breast aside for future use. Pick the meat from the back of the carcass and add to 2 1/2 cups of the stock. Season and thicken slightly. Now place the legs and wings in a casserole dish and add peas, the prepared gravy, and boiled onions. Cover with a crust of plain pastry and bake in a moderate oven for thirty minutes.