Preheat oven to 400°F. Sift together the flour and baking powder. Cream sugar and butter and add the egg. Add the sifted dry ingredients and mix to a smooth dough.
Roll into small balls and place on greased cookie sheets 1 inch apart. Flatten criss-cross style with a fork dipped in flour. Brush with beaten egg white and sprinkle with chopped nuts. Bake for 10 to 12 minutes.