Heat oven to 350°F. Combine butter, sugar, egg yolks and vanilla in large bowl. Beat at medium speed, scraping bowl often, until well mixed. Add flour and salt; beat at low speed, scraping bowl often, until well mixed.
Shape dough into 1-inch balls. Place 2 inches apart onto ungreased cookie sheets. Flatten balls to 1/4-inch thickness with bottom of glass dipped in sugar. Place pecan half in center of each cookie.
Bake 10-12 minutes or until edges are lightly browned. Cool 1 minute on cookie sheets; remove to cooling rack.
Cookies can be flattened with decorative cookie stamp instead of glass.