Preheat oven to 325°F. Line baking sheets with parchment paper or silicone baking mats. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, combine the melted butter, egg yolk, ¾ cup powdered sugar, and salt.

With the mixer on low speed, gradually add 5 cups of the all-purpose flour. Continue mixing on low speed for 15 minutes, scraping the sides of the bowl as needed.

Add the almond meal and almond extract. Return the mixer to low speed and mix for another 15 minutes.

In the last few minutes of mixing, if the dough is too soft to form into a ball, add the last cup of flour, ½ cup at a time, until the dough can be shaped.

Working with 1.5-tablespoon portions, shape the dough into crescents and place on the lined baking sheets.

Bake for 13-14 minutes, until the cookies are pale, the outsides are dry, and the bottoms are set.

Let rest on the baking sheet for 5 minutes. Very carefully remove each cookie from the baking sheet and coat in the remaining powdered sugar. Cookies are very delicate, so be very gentle.

Let the cookies finish cooling on a wire cooling rack. When completely cool, coat the cookies one more time in powdered sugar.