Cream butter with sugar and vanilla until light and fluffy (use electric beater). Gradually beat in flour. Shape into walnut size balls and flatten out with a flat bottomed glass dipped in flour, on an ungreased cookie sheet. Bake at 325 degrees for 10-15 minutes. (watch as they can brown easily) Frosting: Mix the butter, powdered sugar, enough milk for consistency and vanilla to taste. Frost the cooled cookie. Then place a pecan half on top.