BAKE at 350 degrees for 15 to 20 minutes. MAKES about 2 dozen cookies. Sift together flour, baking powder, and salt. Cut in butter until particles are the size of small peas. Sprinkle 3 to 4 tablespoons beaten egg over flour mixture, stirring with fork to form a dough. Roll out on floured surface to slightly less than 1/8-inch thickness. Cut into 3-inch rounds. Fit into small paper baking cups (tea size cups). Place on baking sheets. Chocolate Filling: Melt semisweet chocolate pieces in top of double boiler over boiling water. Stir in sugar, milk, butter, and vanilla; remove from heat. Blend in 1 beaten egg. Place a scant tablespoonful of filling in each pastry shell. Top with a pecan half. Bake in moderate oven (350 degrees) 15 to 20 minutes. *For use with Pillsbury's Best Self-Rising Flour, omit baking powder and salt.