Sour Cream Cookie Dough:
In a large mixing bowl beat 1/2 cup butter, softened, with a mixer on medium to high for 30 seconds. Add 1/2 cup sugar, 1/2 teaspoon baking powder, 1/8 teaspoon baking soda, and a dash of salt; beat until combined. Add 1 egg yolk, 1/4 cup sour cream, and 1 teaspoon vanilla; beat until combined. Beat in 2 cups all-purpose flour. Divide dough in half; wrap and chill, if necessary, until easy to handle.