Step 1

Cream together the butter and sugar in a large bowl with an electric mixer for 2-3 minutes until light and fluffy.

Step 2

Add the sour cream, eggs, and vanilla and mix until well combined. Gently mix in the flour, baking soda, baking powder, and salt. Mix until just combined. Refrigerate overnight to firm up.

Step 3

Preheat the oven to 350°F. Line two large baking sheets with parchment paper and set aside.

Step 4

Scoop the chilled dough into 1 inch balls and space 2 inches apart on the prepared baking sheets.

Step 5

Bake for 11-12 minutes until the center is soft and the edges are just beginning to brown.

Step 6

Allow the cookies to cool for 5 minutes on the baking sheet before transferring to a cool rack to cool completely.

Step 7

To make the buttercream frosting, cream the butter for 3-5 minutes with an electric mixer until light and fluffy. Slowly beat in the powdered sugar until the buttercream is smooth. Add the milk and vanilla and mix to combine.

Step 8

Frost the cookies if you wish or leave them plain, or dipped in icing sugar.