Heap the macarons in a bowl and smash them into a coarse crumb. Strew two-thirds of the crumb in the bottom of a handsome dish. Put the remaining third to one side. Libate the coarsely crumbed macarons in the dish liberally with two-thirds of the sherry or cognac, putting to one side the remaining third
Place the softened butter and sugar in a bowl and mix thoroughly until pale. Add the egg yolk and mix well
Pour the milk into a pan, place over a moderate heat and bring to a simmer. Remove the pan from the heat, tip in the chocolate and stir until the chocolate has melted completely, becoming smooth. Pour this on to the beaten butter, sugar and egg yolk. Mix this all together thoroughly. Decant the chocolate mixture on to the macarons drenched in cognac
Strew the remaining macarons atop the chocolate, pour over the remaining cognac and press the macarons so very gently with your fingertips into the surface of the chocolate. Cover and refrigerate for at least 6 hours, or, better still, a few days in advance