Whisk the ground hazelnuts, sugar and baking powder together in a medium sized bowl. Drizzle the vanilla extract and amaretto liqueur on top and whisk again to combine.
In the bowl of a stand mixer or medium bowl with hand held mixer, beat the eggs whites until soft peaks form. Gently fold the egg whites into the nut mixture until completely combined. Cover and chill the dough in the fridge for 1 hour.
Preheat the oven to 325 degrees F. Line two large baking sheets with parchment paper.
Remove the dough from the fridge and roll it into 1 inch balls, toss in the extra sugar for rolling and place the balls 2 inches apart on the baking sheets.
Bake for 15 minutes or until the cookie bottoms are golden brown. Cool on the baking sheet for a few minutes before transferring to cooling rack to cool completely. Store in an airtight container.