Hazelnuts are also called filberts. They have a brown skin that can be removed by heating them at 350 degrees for 10 to 15 minutes until the skin begins to flake. Place a handful of hazelnuts in a dishtowel, then rub vigorously until most of the skin is removed. Ancient Greeks believed hazelnuts could treat coughing and baldness.
Macadamia nuts are never picked. They are harvested from the ground after they fall off the tree. They also have the hardest shell of any nut, taking 300 PSI of pressure to crack it open.
We really do love that curve to the cashew, and so do other countries. In Iran, the cashew is known as the "smiling nut" and "happy nut" in China. No wonder they cheer us up.