Instructions

• Preheat oven to 170°F (the lowest setting on most ovens). Line a rimmed baking sheet with parchment paper. Spread the sifted almond flour and sifted pistachio flour in an even layer on the sheet.
• Bake the nut flours at 170°F for 30–45 minutes, stirring or shaking the pan once or twice, until the flours are dry and lightly toasty. This removes excess moisture so the cookies hold their shape. Let the flours cool completely on the baking sheet.
• Once cooled, transfer the dried nut flours to a large bowl.
• Increase oven temperature to 300°F. Prepare your baking sheet(s): stack two matching, heavyweight, light- to medium-colored cookie sheets one inside the other if you have them (this helps prevent excessive browning), and line with parchment paper or a silicone baking mat. If you do not stack sheets, use a single lined sheet and watch baking time closely.
• Add the granulated sugar (1 cup) and 1/4 teaspoon salt to the cooled nut flours and whisk until evenly combined.
• In a clean mixing bowl or the bowl of a stand mixer fitted with the whisk attachment, combine the 2 large egg whites and 1/2 teaspoon lemon juice. Whisk until the egg whites hold soft peaks.
• Add the beaten egg whites and 1/2 teaspoon pistachio extract to the dry ingredients. Stir until the mixture forms a soft, sticky dough; if needed, gently knead with your hands to bring it together.
• Lightly dust your hands with confectioners’ sugar. Use a small cookie scoop to portion the dough into 1-inch balls. Roll each portion into a smooth ball, then roll each ball in confectioners’ sugar to coat.
• Arrange the coated balls on the prepared baking sheet, leaving about 1 inch between cookies.
• Bake at 300°F for 30–35 minutes, until the tops are cracked and the bottoms are just barely golden. If you did not use doubled cookie sheets, begin checking at about 25 minutes because they may brown sooner. For crunchier cookies, bake an additional ~5 minutes or until the tops begin to brown.
• Remove the cookies from the oven and let them rest on the baking sheet for a few minutes. Transfer cookies to wire racks to cool completely.
• Store cooled cookies at room temperature in an airtight container or bag for up to 5 days.