Preheat your oven to 350° and line 2 baking sheets with parchment or a silicone baking mat.
In a medium bowl, whisk together the flour, baking powder, baking soda and salt. Set aside for a moment.
In the bowl of your stand mixer, fitted with the paddle attachment, combine the butter, sugar and sour cream together until well combined. Next add in the eggs, one at a time and mixing after each one. Then add in the vanilla and mix until incorporated.
With your mixer on low, slowly add the flour mixture, scraping down the sides and bottom of the mixing bowl halfway through.
Using a 2-tablespoon scoop to measure 12 cookies (per baking sheet) out and placing them onto the prepared pan. Roll each cookie dough into a ball and use your fingers to press flat -- about 1/3-inch thick, the will still rise quite a bit in the oven.
Bake for 10 to 12 minutes or until the edges are barely golden brown. Remove and let cool on the pan for 5 minutes before transferring to a wire cooling rack to cool completely before frosting.
FOR THE FROSTING:
Start by adding a stick of super soft (not melted) butter to your stand mixer and blend until smooth and creamy. About 2 minutes.
Next add in the sifted powder sugar and mix until combined. Add in the vanilla and enough milk until the frosting has reached the desired consistency. Add drops of food coloring --if using-- until you get the color you're after.