Place the egg whites in a large mixing bowl, and allow to sit at room temperature for 30 minutes.
In a separate bowl, whisk together the hazelnuts, flour, cinnamon, and cloves. Set aside.
Using an electric mixer on high speed, beat the egg whites until soft peaks form.
Slowly add the sugar (over 1-2 minutes), beating until stiff peaks form.
Carefully fold the hazelnut mixture into the egg white mixture. Cover and let stand for 30 minutes.
Preheat oven to 325°F (160°C). Line baking sheets with parchment paper or silicone liners.
Drop the dough onto the prepared pans, using about 1 to 1 & 1/2 teaspoons at a time. (I use a scoop for easier portioning.)
Bake 10-12 minutes or until the edges are lightly browned and the tops appear dry and set.
Cool on the pans for 10 minutes. Then transfer to a wire rack to cool completely.
Spread the bottom of each cookie with melted chocolate. Place upside down and allow the chocolate to set.
Notes
*To toast hazelnuts, place them in a single layer on a lined rimmed baking sheet. Bake at 350°F for about 10 minutes. After cooling, use a towel to rub the hazelnuts to remove the skins. They can then be ground in a food processor or blender.