Steam Brussels Sprouts in a large pot of salted water for 6 minutes to partially cook. Drain Brussels Sprouts.
Meanwhile, heat the oil in a heavy large skillet over medium heat. Add the garlic and onion; sauté until golden, about 2 minutes. Add cooked pancetta and the Brussels Sprouts to the same skillet and sauté until heated through and begin to brown, about 8 minutes.
Season with salt & pepper to taste. Serve and enjoy.