Beat butter at medium speed with an electric mixer until creamy. Add flour and next 5 ingredients, beating at low speed until blended. Stir in chopped pecans. Wrap dough with plastic wrap; chill 1 hour.
Shape dough into 2 (9-inch-long) logs. Wrap in plastic wrap, and chill 1 hour.
Cut dough into 1/2-inch-thick slices. Place rounds on lightly greased baking sheets; top each round with a pecan half.
Bake at 350° for 25 minutes or until lightly browned; remove to wire racks, and let cool completely.