In a large mixing bowl cream the butter with a blender for 2 minutes. Add both sugars and cream for 2 more minutes. With a spoon, mix in peanut butter and egg.
In a separate bowl, mix together dry ingredients: flour, baking soda, baking powder, and salt. Stir dry ingredients into the sugar/butter mixture. Wrap dough in plastic and refrigerate at least 3 hrs.
Preheat oven 375 F. Shape dough into small 2inch balls. Place about 3inches apart on ungreased cookie sheet. slightly flatten with a fork in a criss-cross pattern. Bake until light brown, about 7-10 minutes. Cool on baking sheet a few minutes, otherwise cookies may break. transfer to baking rack to cool completely.