Step 1

Preheat the oven to 350°F (175°). Line two baking sheets with parchment paper and set aside.

Step 2

Make the cookies. In a large bowl, beat the butter and sugars with an electric mixer until light and fluffy. Beat in the eggs and yolks one at a time, then stir in the vanilla and buttermilk.

Step 3

In a separate bowl, whisk the flour, baking powder, baking soda, and salt. Gradually add the dry ingredients to the butter mixture, stirring by hand until just incorporated. Stop mixing when no streaks of flour are visible.

Step 4

Drop 2 tablespoonfuls of dough onto the prepared baking sheets, spacing each cookie about 2 inches apart. Bake for 10-12 minutes until the edges are lightly browned. Let cool on the baking sheets for 10 minutes before transferring to wire racks to cool completely.

Step 5

Make the glaze. Melt the butter and brown sugar in a saucepan over low heat, stirring constantly. Stir in the salt and buttermilk, remove the pot from the heat, then whisk in the powdered sugar, 1/4 cup at a time, until smooth. Add as much as needed to reach the desired consistency.

Step 6

Spread or drizzle the glaze over the cooled cookies and let the glaze set before serving. Enjoy!