Cut off the tough ends of the asparagus so that all the spears are about 6 to 7 inches long; you should have about 10 ounces trimmed asparagus. Combine the balsamic vinegar, lemon juice, Dijon, and honey in a small bowl; set aside. Heat 1 tablespoon of the oil in a 10-inch straight-sided saute pan over medium-high heat. Add the pancetta strips and cook, stirring frequently, until browned and crisp, 2 to 3 minutes (don't let them burn). Take the pan off the heat and transfer the pancetta to a plate, leaving behind as much fat as possible.

Return the pan to medium-high heat, add 1 tablespoon of the butter to the fat in the pan and swirl to melt (there will be browned bits on the bottom of the pan). Add the onions and a pinch of salt and saute until nicely browned on all sides and beginning to soften, 2 to 3 minutes. Take the pan off the heat and transfer the onions to another plate.

Return the pan to medium-high heat and add the remaining 1 tablespoon olive oil, the asparagus, and 1/4 teaspoon salt. Toss well with tongs. Cook without stirring until the bottoms of the spears are nicely browned, 3 to 4 minutes. Toss and turn over, and cook for another 1 to 2 minutes to lightly brown another side. Return the onions to the pan, stir, and pour over the chicken broth. Immediately cover the pan and simmer until the liquid is almost completely reduced, about 3 minutes.

Uncover, add the balsamic and Dijon mixture, stir to coat thoroughly, and cook for a few seconds until it has a glazy consistency. Add the remaining 1 tsp. butter and toss to melt and combine, scraping up any browned bits in the pan with a heatproof spatula or a wooden spoon. Toss in the crisped pancetta. Serve right away as individual servings or pour and scrape the contents of the pan onto a small platter and serve family style.