Heat a large skillet over medium high heat, and add the olive oil. Add the shallots and sauté for 3 minutes until tender.
Add the slivered Brussels sprouts, season with salt and pepper, and sauté for 5 to 10 minutes, until the Brussels sprouts are wilted, or as soft as you would like them. Stir in the balsamic vinegar and let it simmer and coat the Brussels sprouts.
Serve hot or warm, with the bacon and/or Parmesan if desired.