Cream butter in a large mixing bowl; gradually add 1 cup sugar, beating until light and fluffy. Add egg and molasses; beat well.
Sift together flour, soda, salt, and spices; add to creamed mixture, stirring well.
Shape into 1-inch balls; place 2 inches apart on greased cookie sheets. Bake at 350° for 10 minutes or until lightly browned. Remove from cookie sheets, and cool completely on wire racks. Sprinkle with powdered sugar.