This is a quick and easy recipe for delicious chocolate cookies that makes good use of egg whites, which are often left over in recipes that only use egg yolks. Simply mix butter, egg whites, powdered sugar, dry ingredients (cake flour, cocoa powder), and salt, emulsify, pipe out, and bake. There is no need to let the dough rest, and it can be made in a short time, so it is recommended for busy people and beginners. These crispy and rich chocolate cookies are made even more visually appealing by adding chopped pistachios, making them a delightful treat for your home cafe or as a gift.