Come Into My Kitchen - Skillet Chicken With Mushrooms and Caramelized Onions

Ingredients

• 4 tablespoons olive oil
• 2 tablespoons plus 2 teaspoons sherry vinegar
• 2 teaspoons honey
• 1 teaspoon Dijon mustard
• 1/4 teaspoon red-pepper flakes
• Kosher salt and black pepper
• 1-1/2 pounds boneless, skinless chicken breasts, cut into 3-inch pieces
• 2 medium yellow onions, thinly sliced (about 4 cups)
• 3/4 pound cremini mushrooms,stems removed and thinly sliced (about 4 cups)
• Bread or cooked pasta, for serving