Before you start anything else, preheat your oven to 450, wrap your sweet potato in aluminum foil, and put it in the oven for 30-40 minutes, until it's mostly soft and gives easily to a sharp knife.Chop your onion, garlic, and mushrooms while it's baking. I usually just tear the kale up as I'm rinsing it in a strainer. When your sweet potato is done and you can sort of touch it, cut it in half and peel off the skin (this should be easy). Sautee olive oil, onions, mushrooms, garlic, and sweet potato until the onions are translucent. Mix together lemon juice, balsamic, and sugar. Add kale and balsamic mixture. Cook until the kale is wilted and yummy. Season with pepper.