3-5 tablespoons heavy cream (enough to get the consistency you want)
colour - optional
Preheat oven to 350 degrees F and line your baking sheets with parchment paper.
In the bowl of a stand mixer, whisk together the sour cream, oil, sugar, vanilla, egg, and egg yolk until smooth. Set aside.
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.
Scoop 2 teaspoons of dough on your 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 your finished cookies a nice round shape.
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.
Only frost cookies when they are completely cooled. I prefer to frost the cookies just before serving them, so that the icing does not cause a problem when storing them. Store cookies in an airtight container.
In a tall mixing bowl, beat all the ingredients with an electric mixer until smooth.
Store in an airtight container until you are ready to frost the cookies.
Cookies can be rolled in sugar before baking. Just spoon the dough into a bowl of sugar, and roll dough to coat in sugar. Form dough into balls and bake as directed.
Recipe by The Baking Beauties at http://www.thebakingbeauties.com/2012/10/gluten-free-sour-cream-sugar-cookies.html