Cookies

1. In a large bowl with an electric mixer, beat butter and sugar on high until light and creamy.
2. Add eggs, sour cream and vanilla, and beat until smooth.
3. Add baking soda, baking powder, and salt and mix until combined. Add flour and beat on low until no white remains — dough will be soft, almost like cake batter. This is how it should be.
4. Preheat oven to 350 degrees F and line baking sheets with parchment paper. Drop by rounded tablespoons onto baking sheets 2-3 inches apart and bake for 10-12 minutes, until edges are golden and centers are set. They do puff and spread quite a bit so don't make them too big!

Frosting

1. With an electric mixer, beat butter until smooth. Add sugar, vanilla and milk and beat until smooth, adding additional sugar or milk to reach desired consistency (you don't want it too thin!).
2. Color if desired and spread on cooled cookies.