Trim Brussels sprouts. Cut sprouts lengthwise in half, then cut crosswise into thin slices.
Place a large cast-iron or other heavy skillet over medium-high heat. Add Brussels sprouts; cook and stir until sprouts begin to brown lightly, 2-3 minutes. Add oil and toss to coat. Stir in onion, ginger, garlic and salt. Add water; reduce heat to medium and cook, covered, until vegetables are tender, 1-2 minutes. Stir in pepper.
