Trim Brussels Sprouts and cut in half lengthwise. Place sprouts, onions and oil in a saute pan over medium-high heat and cook until browned and tender, about 10 minutes.
Toss with salt, pepper and Parmesan cheese. Drizzle with balsamic reduction.
Serve immediately.
Hack: Frozen brussels sprouts can be used for this recipe. Add sprouts whole and frozen to the saute pan. Allow an additional 5-10 minutes of cooking time.
Hack: ¼ cup chopped fresh or frozen onion can be substituted for the frozen pearl onions.
Hack: Leftovers can be stored tightly covered in the refrigerator for up to 5 days or frozen for up to 3 months.