• In a medium mixing bowl, whisk together the flour, baking soda, baking powder, and salt.
• In a mixing bowl, cream the butter and light brown sugar until light and fluffy, about 4 minutes, scraping down the bowl with a spatula about halfway through.
• Add the eggs, one at a time to the butter and sugar, making sure they are incorporated fully before adding the next.
• Add the root beer concentrate. Then add the sour cream, and mix well. Scrape down the sides of the bowl, and with the mixer on low, gradually add the dry ingredients. Mix until just combined.
• Place two sheets of plastic wrap onto a clean work surface and divide the dough in half, placing each onto the plastic.
• Wrap the dough, and into flat rectangles, about 1 ½ inches in thickness and refrigerate overnight or a minimum of three hours to become firm.
• When ready to bake, preheat oven to 425°F, and prepare two baking sheets by lining each of them with Reynolds Kitchens Parchment Paper.
• Place a sheet of Reynolds Kitchens Parchment Paper with SmartGrid onto a clean work surface, and dust it with flour. The dough will be sticky, so dust both the parchment and rolling paper with some flour. Roll out one of the dough halves so that it is about 1/4 inch thick. Using a round cookie cutter that measures about 2 ½-inches, cut the dough into circles and place onto the prepared baking sheets about 1 inch apart using the gridlines for spacing. Gather scrap pieces, and re-roll the dough to cut out more cookies.
• Bake for about 7-9 minutes until just barely golden. Remove from baking sheets immediately and transfer to a rack to cool completely before frosting. 

Root Beer Buttercream Frosting

• In the bowl of an electric mixer, fitted with the paddle attachment, cream butter, vanilla, and root beer concentrate until light and fluffy.
• With the mixer on low speed, gradually add the confectioners’ sugar and the salt. Frosting will be dry at first, but will gradually become smoother and a bit creamier.
• Add the cream, one tablespoon at a time, incorporating each completely. After mixing in all of the cream, beat on medium-high speed for about two minutes, until light and fluffy.
• Frost cookies and sprinkle with shimmer white sugar crystals, if desired. Allow frosting to set before storing in an airtight container.