Melt-In-Your-Mouth-Cookies

4 cups sifted flour
1 tsp. Soda
1 tsp. Cream of tartar
1 tsp. Salt
1 cup butter, softened
1 cup vegetable oil
1 cup sugar
1 cup powdered sugar
2 eggs
1 tsp. Vanilla

Sift flour and then measure out the 4 cups. Mix together the flour, soda, cream of tartar and salt. Set aside.
Beat butter, oil and sugars together until they are creamy. Add eggs and vanilla. Add dry ingredients.
Chills mixture 1 hour and roll into balls. Bake on ungreased cookie sheet at 350 degrees until lightly browned. Makes about 10 dozen.