Preheat oven to 375° F. In a large mixing bowl beat peanut butter, shortening and margarine with an electric mixer about 30 seconds or until combined. Add half of the flour, the brown sugar, 1/2 cup sugar, egg, vanilla, baking powder and soda. Beat until thoroughly combined, scraping sides of bowl occasionally. Beat or stir in the remaining flour. If necessary, cover and chill dough until easy to handle, about half an hour. Shape dough into 1-inch balls. Place 2-inches apart on an ungreased cookie sheet. Using the tines of a fork dipped in the sugar, flatten balls to about 1/4-inch thickness by pressing fork in two directions to form criss-cross marks. Bake in a 375° F. oven for 9 to 11 minutes or until edges are lightly browned. Transfer to a wire rack; cool. Makes about 4 dozen cookies.