Preheat oven to 300°F. Line baking sheets with parchment.

In a large skillet over medium heat, toast pistachios for 7 to 9 minutes, or until fragrant and light brown.

Place pistachios and sugar in the bowl of a food processor and run until nuts are finely ground.

With the machine running, add egg whites and almond extract, and process until a dough forms.

Transfer to a piping bag with a 1/4 inch opening or tip.

Pipe 1 1/2 inch disks on baking sheets, leaving at least an inch of space between cookies.

Sprinkle with powdered sugar and bake for approximately 20 minutes, rotating from top to bottom and front to back halfway through, or until stiff on the edges and slightly soft in the center.

Let cool on baking sheets for 5 minutes, before transferring to a a rack to cool completely.

Store in an airtight container.