Cream the butter and sugar together until very light; add the yolks well beaten; then the almonds blanched and cut in strips; mix; add the vanilla and stir in lightly the flour. The dough should be rather soft. Take a small piece at a time, drop it in powdered sugar, and roll it between the hands into a ball one inch in diameter. Put a piece of pistachio nut on the top. Place the balls a little distance apart on floured pans, and bake in a moderate oven ten to fifteen minutes, or to a pale color. They will flatten in baking and have the shape of macaroons.