Preheat oven to 270 degrees F. Line cookie sheets with parchment paper.
Using an electric mixer at low speed, cream the butter and sugar until smooth. Beat in the vanilla. At low speed gradually add the flour. Mix in the pecans with a spatula.
With floured hands, take out about 1-tablespoon of dough and shape it into crescent. Place the cookies 1-inch apart on the prepared cookie sheets. Cook's Note: Continue to dust your hands with flour as you make more cookies.
Bake for 40 minutes. Dust with additional confectioners' sugar while still warm. Cool completely on wire racks and store in airtight containers.