Wipe young saffron milk-caps dry and fry them in a large quantity of butter, but do not overcook them or let them dry out. Cool the mushrooms, stand them upright in a jar (as they grow with the caps on top), and pour on that same barely warm butter in which they were fried. The butter should completely cover the mushrooms and extend above them to a width of 3 or 4 fingers. Tie a bladder round the jar and store in a dry, cold place. Refry lightly when using the mushrooms in winter.