Brussels Sprouts with Caramelized Onions

Bring a large pot of salted water to a boil. Add the Brussels sprouts and cook until al dente, about 6 minutes. Drain and rinse under cold water. Dry and cut in half.Heat the oil in a large skillet over medium-high heat. Add the pancetta and saute until crisp, about 10 minutes. Transfer the pancetta with a slotted spoon to a plate. Add the onion to the fat in the pan, reduce the heat to medium-low, and cook, stirring frequently, until the onion is soft and browned, 15 to 18 minutes. Add the Brussels sprouts to the skillet and stir gently until warmed through, 6 to 8 minutes. Return the pancetta to the skillet. Season with salt and pepper. Serve warm.