Alice Medrich shared this nifty trick with Julia Child years ago and it's a keeper. You blanch, or quickly dunk in boiling water, the hazelnuts. But you want to add some baking soda to the water. Use 2 cups boiling water and 3 tablespoons baking soda. Toss in the hazelnuts and boil for 3 minutes. The water may turn dark. Don't freak out. Pour the hazelnuts and their boiling water into a colander placed in the sink and rinse under cool running water. The skins should slip right off.