Trim outer leaves and stems from brussels sprouts, and discard. Bring a medium pot of water to a boil, and add a few dashes of salt. Meanwhile, prepare an ice-water bath. Add brussels sprouts to boiling water, and cook until tender but still bright green, about 4 minutes. Remove from heat, drain, and plunge into ice-water bath to cool. Drain well, and cut in half.
Heat 1/2 tablespoon butter and 1/2 tablespoon Lucero Olio Novello in a large heavy skillet over medium-high heat. Add brussels sprouts, and cook, tossing occasionally, until they are brown and crisp on the edges, about 3 minutes. Season to taste with salt and pepper, and transfer to a large bowl. Cover with aluminum foil to keep warm.
Add remaining 1/2 tablespoon each butter and Lucero Olio Novello to the same pan over medium-low heat. Add onions, and cook, tossing occasionally, until wilted and transparent, about 3 to 4 minutes. Add Lucero Mission Fig Balsamic Vinegar, and stir to loosen any brown bits on bottom of pan. Cook until Balsamic Vinegar is reduced and the onions are glazed, about 30 seconds.
Add onions to brussels sprouts, and toss well. Serve immediately.