Preheat oven to 350 degrees.
Measure the dry ingredients together in a small bowl. Combine flour mixture, set aside.
Using an electric mixer, cream butter and sugar.
Add the egg and vanilla, mix again until creamy.
In a medium bowl, add the dry ingredients to the butter mixture and mix to combine, If using the nuts, stir them in at the end by hand.
Drop the cookie dough balls by teaspoons onto the prepared baking sheet lined with parchment paper, bake for about 10 minutes.
Remove from sheet pan and transfer to a wire rack. Cool to room temperature.
For the frosting - When the cookies are done baking, make the brown butter. Brown slightly.
Using a stand mixer, beat the vanilla and powdered sugar. Slowly add the brown butter. Beat until light and fluffy.
Frost the cookies and dust with sprinkles if desired