In a 6-quart stockpot, cook the sausage and onion over medium heat. With a wooden spoon or spatula, break the sausage into crumbles and cook until it's no longer pink, about six to eight minutes. Remove the sausage and onions with a slotted spoon and set aside.
Add the kale to the pot. Cook, stirring often, for about two minutes, allowing the greens to soak up some of the oil from the sausage and onions. Add the garlic and pepper flakes and cook for one minute. Add the wine, if using, and cook two minutes longer. Editor's Tip: Be careful not to burn the garlic, which gives it a bitter flavor.
Stir in the sausage mixture and remaining ingredients. Bring to a boil, then reduce the heat to a simmer. Cook, covered, until the kale is tender, about 15 to 20 minutes.
