In saucepan, cover Brussels sprouts with water, add salt, and bring to boil; remove immediately and strain.
In stainless-steel bowl, combine oil, onion, and seasonings with Brussels sprouts.
On prepared grill, grill until completely charred, turning for even cooking. (I recommend a perforated grill pan, and use it like you’re stir-frying sprouts on the grill.)
For Dijon vinaigrette, in stainless-steel bowl, whisk together mustard, vinegar, and oil. Add Brussels sprouts and toss.
To serve, place on a platter and drizzle with Balsamic Syrup (see recipe here