Prepare Crêpes. Tie up 1½ glasses rice in a cloth and boil in salted water until half-cooked so the grains remain separate. Choose a saucepan the same size as the crêpes, butter the pan, and strew it with rusk crumbs. Stack the finished crêpes in the pan, covering each one with some rice, a few small pieces of bone marrow (mozgi iz kostej), and some currants. Cover with the saucepan lid and bake. Serve separately sugar or brown sauce.