In a large bowl, whisk together flour, baking powder, baking soda and salt. Set aside. 

In the bowl of a standing mixer fitted with the paddle attachment, beat the butter and sugar on medium-high speed until light and creamy (about 2 minutes). Use a rubber spatula to scrape down the sides and bottom of the bowl as necessary. Mix in egg, sour cream, almond extract and vanilla extract on medium-speed.

Turn the mixer down to low and gradually add dry ingredients. Mix until fully incorporated. Cover with plastic wrap and chill for at least one hour or overnight. 

Preheat oven to 350F. Line baking sheet with parchment paper. Set aside. 

Remove dough from refrigerator. Scoop heaping tablespoon and place on prepared baking sheet. Repeat, making sure cookies are about 3 inches apart. 

Bake for 13 – 15 minutes, until the top is springy to the touch. Remove and let cool for 5 minutes on the baking sheet before transferring to a cooling rack to cool completely. 

In the bowl of a standing mixer fitted with the paddle attachment, beat the butter on medium speed until smooth and creamy. Turn the speed down to low and alternately add powdered sugar and heavy cream until combined. Add almond extract and salt, then mix on medium-high for 2 minutes until fluffy. 

Pipe or spread on top of cooled cookies. Add sprinkles if desired.