Preheat oven to 375F.
Heat the olive oil in a large, nonstick skillet on high heat. Add the kale (leaves only, no woody stems) and saute 1 minute. Add the water and cook, stirring until the water has evaporated and the kale is nice and wilted. Add the garlic and saute briefly until garlic is lightly browned and kale is just slightly charred. Remove to a cutting board and chop finely.
In a bowl, combine the evaporated milk, cornstarch, salt, pepper, and nutmeg.
In another bowl, toss together the cauliflower and finely chopped kale. Transfer to a baking dish sprayed with olive oil. Pour the milk-cornstarch mixture over the veggies. Top with the cheeses. Lastly, top with a very light layer of cashews.
Take a piece of foil large enough to cover the casserole and spray one side with cooking spray. Put the foil over the casserole, oil-sprayed side down, and wrap to cover the gratin. Bake 30 minutes at 375F. Remove the foil and continue baking another 20-30 minutes until the cauliflower is tender and the top of the gratin is bubbly and lightly browned. If there is excess liquid at this point, simply spoon or siphon it off. Let stand 10 minutes before serving. Yield: 4 servings.