Heat a large skillet over medium-high heat with 2 turns of the pan of EVOO, about 2 tablespoons. Add pancetta and cook until crisp, about 4 minutes.
Add the onion, and season with salt and pepper. Cook, stirring occasionally, for 2-3 minutes.
Add the sprouts along with the chicken stock and the balsamic vinegar.
Stir to combine and continue to cook for 10-12 minutes or until the Brussels sprouts are tender.