In a large, heavy saucepan or Dutch oven, heat the oil over medium-high heat. Add the pancetta, onion, and red chile flakes; sauté until the onion is deep golden, about 5 min. Add the kale; toss with tongs to coat the leaves with oil. Add the chicken broth and bring to a boil. Cover, reduce the heat to medium low, and simmer until the leaves are quite tender, about 10 min. (thicker-leaved varieties will need longer, so do check the pan, adding water or broth if needed, and taste a leaf).
Stir in the minced garlic, raise the heat to high, and boil uncovered until the pan is dry. Season with a few grinds of pepper (you probably won't need salt) and serve.
nutrition information (per serving):
sat fat g