Using a stand mixer with a paddle attachment (or a hand mixer), add the powdered sugar and salt to the bowl and mix to combine.
1 cup powdered sugar, ½ tsp. salt
Add the cold butter pieces and beat on low to start, then increase the speed. Beat until the butter and sugar form almost like a paste. Scrape down the sides of the bowl as needed.
1 cup unsalted butter, cold, cut into cubes
Add in the egg, egg yolk, vanilla extract and almond extract (if using).
1 large egg, 1 large egg yolk, 2 tsp. vanilla extract, ¼ tsp. almond extract
Add the flour and baking powder and mix just until combined. If the dough seems dry, add a splash of milk.
2¾ cups all-purpose flour, 2 tsp. baking powder, 2-4 tsp. milk
Divide the dough in half.
Place each half of dough on a sheet of parchment paper. Place a second sheet of parchment paper on top of each half of dough.
Using a rolling pin, roll out each half of dough between the 2 sheets of parchment until ~⅜ inch thick. (Tip: ⅜ inch thick is right in between ¼ and ½ inch thick.) I like them a little thick, so they have a nice chew!
Then, freeze the dough until cold (20-30 minutes or longer if needed).