Heat molasses to boiling point and pour over shortening. Add dry ingredients mixed and sifted. Chill thoroughly. Toss one-fourth of mixture on a floured board and roll as thinly as possible; shape with a small round cutter, first dipped in flour. Place near together on a buttered sheet and bake in a moderate oven. Gather up the trimmings and roll with another portion of dough. During rolling, the bowl containing mixture should be kept in a cool place, or it will be necessary to add more flour to dough, which makes cookies hard rather than crisp and short.