Kale's distinctive flavor is mellowed by the addition of bacon and a splash of balsamic vinegar. The bacon lends a smoky nuance and the balsamic adds a note of sweetness to complement the kale's hearty flavor. Chances are, even if you don't like kale, you'll be a fan of this dish!
Place the bacon in a large skillet, preferably nonstick, and cook over medium heat until the bacon is crispy and brown. Remove the bacon with a slotted spoon and set aside to drain on paper towels.
Add the shallots, garlic, and red pepper flakes to the bacon fat in the skillet and sauté over medium heat for 2 minutes, stirring frequently.
Add the kale and chicken stock, and raise the heat to medium-high. Cover the pan and cook the kale for 10 minutes. Remove the lid and continue cooking the kale until it's tender and the liquid has evaporated, 10 to 15 minutes.
Stir in the bacon and season to taste with salt and balsamic vinegar. Serve immediately.