Hazelnuts, also known as filberts usually work best in a recipe when their skins are removed. This is because the skins are bitter and they can alter the look of the final product based on their dark color. There are two ways to skin hazelnuts: the old way and the new way. The old way involves toasting the hazelnuts, wrapping them in a towel and rubbing the skins off. This method doesn't really remove all of the skins, most of which get embedded into the towel. Nice hazelnut towel you've got there. Now for the new method.
The new method involves the power of baking soda and boiling water that allows the skins to slip right off. The downside of this method is that it requires you to boil the hazelnuts then remove the skins with your fingers on each individual nut. Who has time for that? People who want to do the job right, that's who. This method removes all skins from your hazenuts.
Preheat your oven to 350F (177C). For every ½ cup of hazelnuts, add the nuts, 1 ½ cups water and 2 Tablespoons baking soda to a medium saucepan and bring to a boil. Boil for 3 minutes. The water will turn black from the skins. To test if the nuts are done, run one under water and see if the skin slips off easily. If it doesn't boil the nuts for another minute and test again.
Transfer the nuts to a colander to drain, cool with cold water and slip the skins off with your fingers. Blot dry, transfer them to a baking sheet and toast them in the oven for 10 to 12 minutes. If you're using the hazelnuts immediately, the toasting step can be omitted.