01 - Preheat oven to 425°F. Line a large baking sheet with parchment paper.
02 - In a small bowl, whisk together balsamic vinegar, olive oil, honey, Dijon mustard, Italian herbs, salt, and black pepper.
03 - Place chicken breasts in a large mixing bowl. Add half of the balsamic mixture and toss thoroughly to coat. Allow to marinate while preparing vegetables.
04 - On the prepared baking sheet, toss cauliflower florets, sliced red onion, and minced garlic with the remaining balsamic mixture. Spread evenly in a single layer.
05 - Nestle the marinated chicken breasts among the vegetables on the baking sheet.
06 - Roast for 25 to 30 minutes or until chicken is cooked through (internal temperature reaches 165°F) and cauliflower is golden and tender.
07 - If desired, broil for 2 to 3 minutes at the end for additional caramelization.
08 - Garnish with chopped parsley before serving.