To Toast Sesame Seeds: Pour seeds into a pie pan and place in a 300 degrees F (150 degrees C) oven for about 10 minutes or until lightly browned. Stir seeds occasionally.
Cream the butter or margarine with the vanilla until light and fluffy. Add the confectioners' sugar gradually, beating until fluffy. Add egg and beat thoroughly.
Sift the flour, baking powder and salt together. Add in thirds to the creamed mixture. After each addition of the flour mixture stir in the toasted sesame seeds. Mix until blended. Cover and chill dough for at least 2 hours.
Preheat oven to 350 degrees F (175 degrees C).
On a lightly floured surface, roll 1/3 of the dough at a time to 1/8 inch thick. Cut with a 2 inch scalloped cutter. Transfer cookies to ungreased cookie sheets.
Bake at 350 degrees F (175 degrees C) for 10 to 12 minutes.