Every time I make kale chips, people drool over them and ask for my recipe. These are the crispy, crinkly, curly kale chips you see for sale in health food stores. Often they are labeled as "raw," which means they were heated at temperatures below 118 Fahrenheit, or thereabouts. They usually cost about 8 bucks for a few meager, crumbly leaves. I have to admit, they can be a little labor intensive to make yourself, but they are so inexpensive and totally worth the time and effort.
The most BASIC recipe can be summed up like this: Take a big bunch of curly kale (preferably two bunches, since it does shrink down a lot). Wash it well and dry it, and remove all the spines. Add just enough olive oil to very lightly coat all the leaves, and massage the oil into every nook and fold of the leaves. Then add salt and pepper to taste. Be careful with the quantities of oil and seasonings, because they will all intensify as the kale heats up and shrinks down. Use just enough to relax the rigidness of the leaves. You don't want it to come out unpleasantly oily, salty or spicy.
It's rather important to use the curly kind, since the little curls crisp up so well, but you could any kind of kale, and in fact you could you use chard, spinach, or any other leafy green -- but in my experience, kale is by FAR the best, and curly kale is best of all.
Then, you cook it. This can be done in an oven at its lowest setting (about 200 degrees). It should take an hour or two at the very most, probably less. Just lay the leaves on trays in one layer. When they are wilted and starting to dry out, turn all the leaves over and put them back in the oven till they're totally dry and crispy. Keep an eye on them -- if you burn them, it's all over.
Now, for my REAL recipe: I soak about 3/4 cup of raw cashews in water for 2 to 4 hours. Then drain and put the cashews in a mini-blender. I add half a peeled red bell pepper, roughly cut, a clove or two of garlic, a tablespoon of nama shoyu or soy sauce, a tablespoon of olive oil, three heaping tablespoons of nutritional yeast, a touch of cayenne or smoked paprika (optional), and a bit of salt and pepper. I blend all that into a creamy and smooth marinade, then massage THAT into the two bunches of kale leaves, in batches. It's amazing.