- Preheat oven to 350 F.
- In a large bowl, beat brown sugar with butter until light and fluffy.
- Add vanilla extract and egg yolk, blend well. Add flour; stir until mixture forms a smooth dough.
- Drop dough by rounded teaspoonfuls, 2-inches apart onto un-greased cookie sheets.
- Bake for 10 to 15 minutes or until lightly browned and set.
- Allow to cool completely then serve!