For a brief while, we had a great little restaurant called Virtù up next to Dianne’s on Divine (which is now also closed) that had the best brussels sprouts in town. Below is what I’ve come up with as a kind of pale imitation thereof. (BTW, Il Giorgione, which now inhabits Virtù’s old space, is well worth a visit.)
Steam 3 sprouts per person until tender.
While they are steaming, thinly cut one slice of red onion per person and start to sauté in a pan with plenty of room.
When the onions have started to clarify, the sprouts should be tender. Remove them from the steamer, remove any coarse outer leaves, cut the sprouts in half, and put them flat side down into the pan with the onions.
When the onions start to brown, push them to a side of the pan away from the heat. Move them from time to time to keep them from burning.
When the sprouts have started to brown on the flat side side, flip them over. When they start to brown on their tops, flip them again.
Quickly but gently stir the onions and sprouts in together and splash some balsamic vinegar over them. Let the balsamic reduce a bit an infuse the veggies with its flavor.
S&P to taste.
When I'm doing this for just myself, I also crisp up a half strip of bacon and crumble it in while the balsamic is steaming away.