Cream together butter, sugars, spices & salt. Add egg & mix thoroughly. Add molasses & blend. Sift together twice: flour, powder & soda. Add to molasses mixture & stir until blended. Chill well. Preheat oven to 375. Using floured rolling pin, roll dough to 1/4" thick on floured pastry cloth or board. Use a cookie cutter to press out desired shape. Place on greased baking sheets & bake 8-10 minutes.