Preheat the oven to 350° Fahrenheit. Line a baking sheet with silicone liner or parchment paper.
In a large bowl, cream together the butter and sugar until light and fluffy.
Add egg, sour cream, salt, and vanilla extract until fully combined, scraping the sides as needed.
In a small bowl, whisk together all-purpose flour, baking powder, and baking soda.
Add the flour mixture to the large bowl and mix until just combined. Scraping the sides as needed.
Using a cookie scoop or tablespoon, divide the dough into 1-inch balls. Place the dough balls on the baking tray with approximately 2-inches between each ball. Using a flat surface, press down on each ball to create a disc.
Baking for 10 to 12 minutes or until very lightly golden. Remove from the oven and let the cookies rest on the baking sheet for another 5 minutes. Then remove the cookie from the sheet and transfer them to a cooking rack to fully cool.
In a large bowl, whisk together butter, powdered sugar, vanilla extract, salt, heavy cream, and food coloring (or gel).
Spread the frosting on the top of the cooled cookies, the layer should be relatively thin and leave a small border of the cooking on the outermost edge. Decorate with sprinkles as desired.
Notes
If you use salted butter, remove the salt from the recipe.