Put three or four dozen large oysters into a stewpan with sufficient white wine or sherry to cover them and let cook gently until firm. Drain, trim, put them in a basin and season with a little salt and the juice of a lemon squeezed over. Set a mould in a box or tin of powdered ice and pour in a thin layer of warmed jelly. Let this set and then lay oysters symmetrically over it to within one-fourth inch of the edge all round. Pour over sufficient aspic to cover these and allow it to set and then repeat the layer of oysters until the mould is quite full, taking care that the aspic shall cover the last layer of oysters without overflowing. Allow this to stand for an hour in the ice and then dip the mould into hot water, removing quickly, and then turn out onto a cold dish. Garnish round with chopped aspic jelly or ornament with croutons of aspic in two or three colors of brown, red and yellow. Serve with a rich mayonnaise sauce.