Created by KittenCal on May 17, 2013
Step 1: Preheat oven to 175 C (350 F), and line baking sheets with parchment paper.
Step 2: In the bowl of a stand mixer, whisk together sour cream, oil, sugar, vanilla, egg and egg yolk until smooth. Set aside.
Step 3: Place all the remaining dry ingredients in a separate mixing bowl and whisk to combine. With the mixer running on low, slowly add the dry ingredients to the wet ingredients. Mix on medium speed until completely blended.
Step 4: Scoop about 2 teaspoons of dough on baking sheet, leaving 2 inches between cookies to allow for them to expand while baking. Dampen your hands with a small amount of water and roll the scooped dough into a smooth ball. This will give finished cookies a nice round shape.
Step 5: Bake cookies in preheated oven for 12-13 minutes, or until just slightly browned around the outside. Allow cookies to cool for a few minutes before moving them to a wire rack to cool completely.
Step 6: Only frost cookies when they are completely cooled, or frost the cookies just before serving them, so that the icing does not cause a problem when storing. Store cookies in an airtight container.
Step 7: NOTE; Cookies can be rolled in sugar before baking. Just spoon the dough into a bowl of sugar, and roll dough to coat. Form dough into balls and bake as directed.