1: Whisk together all of the Balsamic Marinade ingredients in a medium bowl.
2: Remove 1 tablespoon and add to a large bowl along with tomatoes and asparagus. Toss evenly to coat and refrigerate.
3: Add remaining marinade to a large bag along with chicken. Marinate for 30 minutes to 4 hours.
4: When ready to grill, let chicken sit at room temperature for 15-30 minutes.
5: Grease and preheat the grill to medium heat, 375-450°F.
6: Grill chicken undisturbed for 5-7 minutes per side until cooked through (165°F). Remove and let rest for 5 minutes before slicing.
7: Grease the grill and turn to high heat. Grill asparagus for 2 minutes per side or to desired tenderness. Let cool, then cut on diagonal into 1-2-inch pieces.
8: To make the dressing, bring balsamic vinegar to a boil, then reduce heat to simmer, cooking until reduced by half (about 8 minutes).
9: Whisk in remaining dressing ingredients, adding additional milk if desired for a thinner dressing.
10: Toss spinach, basil, asparagus, tomatoes, and mozzarella in a large bowl. Top with chicken, bacon, and avocado.
11: Drizzle individual servings with Balsamic Reduction Dressing.
