Preheat oven to 200 degrees. Cut 2 pieces of parchment paper to line 2 baking sheets; draw a 9-inch circle onto each parchment (this will be your guide for piping the dacquoise), then turn parchment upside down on baking sheets. Lightly spray parchment with cookie spray; set aside.
Whisk together flour, hazelnuts, 1/4 cup superfine sugar, and confectioners' sugar; set aside. In the bowl of an electric mixer fitted with the whisk attachment, beat egg whites until soft peaks form. One tablespoon at a time, slowly add remaining 1/4 cup superfine sugar; continue to beat until stiff peaks form. Fold in the nut mixture.
Fit an 18-inch pastry bag with a 1/2-inch-diameter round tip, and fill with the nut-meringue mixture. Using the pre-drawn circles as your guide, and starting within the line, began piping nut-meringue around the inside of the circle, continuing until you reach the center of the circle. Keep constant but gentle pressure on the piping bag to make sure there are no holes in the piped circles. Once circles have been piped, gently smooth them over using a small offset spatula.
Bake dacquoise, about 2 hours or until dry. Then, turn off the oven and leave them inside until oven has cooled. Dacquoise can be made several days in advance and stored in an airtight container in a cool, dry place. They may also be frozen for up to 2 months, wrapped well and kept in an airtight plastic container.