Toasted Cashew Cookies With Browned Butter Frosting

Preheat oven to 350 degrees and adjust oven rack to middle position.
Chop by hand or use a food processor to finely chop the cashews until no large pieces remain. Toast the cashews in the oven for about 15 minutes, or until they are deep brown in color. Allow the toasted cashews to cool
In a separate bowl, combine the flour, baking powder, baking soda and salt and set aside. Add the butter and brown sugar to the bowl of a stand mixer and beat on high speed until light and fluffy. Add the egg and the vanilla, beating well to combine. Add sour cream and beat until just comined. Gradually add the flour mixture and gently mix to combine. Fold in the cooled and toasted cashews. Drop by rounded spoonfuls onto parchment lined cookie sheets.
Bake cookies for 12 to 15 minutes until edges are set and the cookies are starting to brown lightly. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.
To make the frosting, melt the butter in a saucepan over medium heat. Cook until the dairy solids in the butter turn dark brown and smell very nutty. Remove from heat and add to powdered sugar. Beat in vanilla. Gradually beat in half & half until smooth and easily spreadable.
Frost the cooled cookies with the browned butter frosting. Allow the frosting to set before covering the cookies.