Originally grown as the filbert in temperate Mediterranean climates, the hazelnut came to the United States in the 1940s. It is slightly larger than its European cousin and is grown in Oregon and Washington, where it is harvested during the fall. Hazelnuts have a bitter brown skin that should be removed before use. Bake in a preheated 350º oven for 10 to 15 minutes, or until the skins begin to flake. Rub the skins off with a kitchen towel, then continue toasting for five minutes, shaking the pan occasionally, to give them a crunchier texture. Store unshelled nuts in a cool, dry place for up to six months. Store shelled nuts in an airtight container in the refrigerator for up to one month, or in the freezer for up to six months.