• In the bowl of a stand mixer, beat the butter and sugar until creamy. Add the egg yolks and extract and beat until smooth.
• In a separate bowl whisk together the flour, cornstarch, milk powder, baking powder and salt.
• Add the dry ingredients to the egg yolk mixture and beat on low with the paddle attachment crumbly. The mixture will be very dry, but it should hold together when you pinch it. Do not overmix with the paddle. Once it starts coming together, use your hands to mix it.
• Empty mixture onto a mat or a large sheet of parchment paper and press down flat, folding it over on itself if you need to to make it a large cohesive slab. Set a piece of parchment paper on top and roll to ¼ inch thickness. Transfer parchment to a tray and refrigerate the rolled dough for about 45 minutes.
• Take out the chilled dough slab and peel away parchment. Use a 2 inch cookie cutter to cut out circles.
• Bake the circles on an ungreased or parchment lined baking sheet at 325 degrees F for about 12 minutes. The tops won't brown, but the bottoms will brown a little.
• Let cool completely before filling.
• Spoon dulce de leche onto half the cookies and sandwich with the remaining halves. At this point you can roll them sideways in coconut if you like, or leave the sides blank. Put the cookies in a container, cover, and let age for a few hours or overnight.
• Dust the cookies with powdered sugar before serving.

Instant Pot Dulce de Leche or Arquipe

• Remove the label and the top from the can of condensed milk, then wrap it in foil. Set the can on a piece of foil and smooth the foil upward onto the sides, then put a piece of foil over the top and press foil downward.
• Set the trivet in the Instant Pot, set the can on the trivet, then add enough water to come halfway up the side of the can.
• Close the Instant Pot, put the dial in the middle, and hit "manual " then 45 minutes and then "manual" again to start. It will take a while to come to pressure, and then you will do a natural release, so plan on about 2 hours for this.
• Carefully remove can from water. Peel away the foil. The dulce de leche will look brown and lumpy at this point. Pour into a glass jar or a bowl. Stir in the butter, vanilla and salt. Stir and stir until it starts to smooth out.