Rinse the pound of chicken skin and fat, pat dry, then chop it into small 1/2 inch pieces.
Place the skin and fat into a nonstick skillet on the stovetop and turn heat to low. Cover the skillet and let it cook on low for about 15 minutes. Liquid fat will start to pool at the bottom of the skillet.
Uncover the skillet and raise heat to medium low. Let it cook for another 15-20 minutes, breaking the pieces apart with a spatula and stirring frequently, until the skin starts to brown and curl at the edges. At this point there should be quite a bit of liquid fat at the bottom of the pan—this is the schmaltz.
Remove pan from heat. Pour the schmaltz from the skillet into a container, using a mesh strainer to catch any small pieces of skin.
After collecting the schmaltz, return the cooked chicken skin and fat to the skillet. Peel the onion, cut it into thin slices and add it to the skillet.
Season the chicken skin and onions generously with salt and pepper. Turn heat to medium and sauté the mixture for about 20 minutes, stirring frequently, until the pieces are dark brown and crispy.
Remove the gribenes from the skillet with a slotted spoon and drain them on a paper towel. Season to taste with salt and pepper.