Preheat a heavy (preferably cast iron) 4-quart pot over high heat to 350o, about 4 minutes. Add the oil and when it begins to smoke, about 4 minutes, add the onions. Cook, stirring occasionally, until they begin to turn golden brown, about 6 minutes, then add the collard greens and the Vegetable Magic®. Scrape the bottom of the pot and cook, stirring occasionally, until the greens are sticking on the bottom and about to burn, about 3 to 4 minutes. Add the mustard greens and cilantro and cook for 1 minute. Add ½ cup stock and scrape the bottom of the pot. The greens will cook down, and the onions will turn dark brown. Cook until all the liquid evaporates, about 10 to 12 minutes, and add the remaining stock. Scrape the bottom of the pot and add the spinach. Stir and cook for 3 minutes. Add the sugar and cook for 1 minute longer. Remove from the heat and serve immediately.