||Preheat oven to 375 degrees. Cream together butter, sugar, egg yolk, and vanilla extract. When this is light and fluffy, add flour, chips, and pecans. Mix well.
Form dough into 1 & 1/2 inch balls and place on an ungreased baking sheet. Dip a glass into sugar and flatten each dough ball. Place a pecan half in the center of each cookies. Bake for 8 to 10 minutes. Cool on wire racks.