Preheat oven to 350 degrees F. Line a rimmed baking sheet with parchment paper.
Break the almond paste into smaller chunks and place in a food processor.
Pulse until the paste resembles crumbs.
Add the sugar and pulse until the mixture is the texture of wet sand.
Add the egg whites to the food processor and pulse until the mixture becomes a solid dough.
Pour the pine nuts into a small bowl.
Divide the dough into 24 portions and roll each portion into a ball.
Press the pine nuts onto one side of the ball.
Place the ball, pine nut side up, on the prepared baking sheet.
Bake for 13-15 minutes, or until the cookies are lightly browned and set.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to cooling racks to finish cooling.
When cookies are completely cooled, dust them with confectioners sugar.
Notes
Sticky Dough: Wet your hands before rolling the pignoli dough so that it is less likely to stick to you.
Not-sticky-enough dough: Try dipping the dough balls into beaten egg whites so that the pine nuts will stick.
Avoid Overbaking: Pine nut cookies are supposed to be nice and chewy on the inside. Bake the cookies just until they turn golden so that they don't come out flat and brittle.
Alternate ingredient: If pine nuts aren't your favorite nut, you can easily substitute them for cashews, pistachios, sunflower seeds and more!