The only tricky thing about meringues is when you make them. Don't bake them when it's especially humid outside, or your meringue cookies may not get as crisp as you'd like. This recipe was written by the Healthline Editorial Team: http://www.healthline.com/health-recipes/hazelnut-meringues —Healthline
Line a large baking sheet with parchment paper. Whisk together granulated and powdered sugar in a small bowl and set aside.
Whip egg whites and cream of tartar in the bowl of an electric mixer at low speed until frothy. Increase speed to medium and beat until soft peaks form; add vanilla and beat to combine. With mixer running, slowly add sugar mixture and beat until stiff peaks form. Gently fold in hazelnuts.
Drop mixture by tablespoonfuls onto baking sheet and slightly flatten with spoon to make cookies uniform in height.
Bake for 90 minutes. Turn oven off, but leave meringues in oven for 2 hours or until crisp. Store in an airtight container.