Combine butter, sugar, egg yolks and vanilla in large bowl. Beat at medium speed, scraping bowl often, until creamy. Reduce speed to low; add flour. Beat until well mixed. Cover; refrigerate until firm (at least 1 hour).

Heat oven to 375 degrees F. Shape dough into 1-inch balls. Place 1 inch apart onto ungreased cookie sheets. Make indentation in center of each cookie with thumb or back of teaspoon. (Edges may crack slightly.) Bake for 7 to 10 minutes or until edges begin to brown. Cool completely.

Combine caramels and whipping cream in medium microwave-safe bowl. Microwave on HIGH (100% power) 1 minute; stir. Continue microwaving 1 minute or until melted; stir until smooth. Spoon about ½ teaspoon caramel mixture into center of each cookie. Top with pecan half.