Preheat oven to 300 degrees F.
Cream butter and sugar together.
Add vanilla and mix well.
Add flour, a little at a time, and mix well until dough forms.
Stir in pecans.
Roll into small balls and place on cookie sheet.
Bake for 20-25 minutes.
Allow to cool on cookie sheet until able to handle. Place powdered sugar into a small bowl.
Using a spoon or your hands, rolls each cookie in powdered sugar and place on rack to continue cooling.
If needed, roll in powdered sugar a second time.
Store in an airtight container.