Source: Mark Bittman

1 large bunch kale (about one pound)
1 tablespoon olive oil
1/2 teaspoon salt
1. Heat the oven to 225 degrees. Trim the ends of the stems from the kale and cut the leaves into three-inch pieces. Toss them with the olive oil and salt, then put them on two baking sheets in a single layer.
2. Cook until slightly shriveled, dehydrated, and sweet but still soft and chewy. You might have to move them or the pan around to ensure they don’t burn or get too crisp. Start testing after about 30 minutes, and remove from the oven when as chewy or crisp as you like, another 10 to 20 minutes. Cool thoroughly before storing in an airtight container.