Once they are baked and cooled, slice them evenly down the middle and take a spoon to scoop out a small amount of the middle. Keep the excess for stews, sauces or breakfast pancakes.
Brush each sweet potato skin with the olive oil, sprinkle with the salt and pepper and half of the onion and garlic powder.
Finely Chop the kale and season it with the remaining onion powder, garlic powder, salt and pepper. Divide the mixture over the 12 skins.
Sprinkle the walnuts over them as well, and then grate fresh parmesan over them.
Bake at 350 until heated through and cheese is melted, about 10 minutes.