Preheat oven to 275 degrees. Cream butter, margarine and sugar together until smooth, slowly add flour until smooth, add pecans and vanilla flavoring. Shape into 1 inch balls. Bake on ungreased cookie sheet at 275 degrees for 1 hour. Yes, you read it right 1 hour. When done, dip the cookies in powdered sugar when they are still warm and again when the cookies cool. Note: I use a zipper bag for my powdered sugar to make it easier and faster to coat the cookies. Enjoy!