In a bowl, add 1 ½ cups all-purpose flour, ½ tsp baking powder, ¼ tsp baking soda, and ¼ tsp salt. Whisk and set aside.
In a large mixing bowl, add softened ½ cup unsalted butter and ¾ cup granulated sugar. Using a hand or stand mixer, beat on a high speed for 3-5 minutes or until the mixture is light and fluffy.
Add 1 egg and 1 tsp vanilla extract and beat again until well incorporated.
Then add ½ cup sour cream and beat again.
Add dry ingredients, and mix on low speed until just incorporated but don’t overmix the dough.
Cover the bowl with plastic wrap and refrigerate for at least 2 hours or overnight.
When ready to bake, preheat the oven to 375F, line a baking sheet with parchment paper and set aside.
Take the cookie dough out of the refrigerator. Using a 1 ½ tbp ice cream scoop or a regular spoon, scoop out the dough and roll it into a ball and place on a baking sheet.
Repeat the same with the rest of the dough and place on the baking sheet 2 inches apart.
Bake at 375F for about 15 minutes or until the bottoms are light golden color and the tops are set.
Take out of the oven and let sit on the baking sheet on the countertop for about 10-15 minutes to cool off and fully set. Then transfer to a wire rack to cool off completely.
When they are completely cooled off, its time to decorate. Add 1 ½ cups powdered sugar in a bowl and gradually add between 1-2 tbsp milk until the the desired consistency.
Top the cookies with the icing and decorate with some sprinkles.