Kale

"Kale is one of the most worthwhile crops you can grow. It is easy, undemanding, tolerant of heat, drought, wet, cold, and poor soil. It can be eaten at the small leaf stage in salads, mid-size leaves are good steamed, and large leaves can be chopped and stir fried or put into stews. One especially good dish is lentil stew with leeks and kale."

So says the this article on kale at Gardens on the Go located here:
Growing Kale

Here's the Farmer's Almanac on Kale:
Kale -- Farmer's Almanac

And this from The National Garden Association
Edible of the Month (from the Edible Landscaping section)