Chicken Pietro

In a small bowl, combine 1/4 cup balsamic vinegar, 1/2 cup olive oil, Dijon mustard, brown mustard, honey, rosemary, water and salt. Whisk together until smooth.

Place chicken pieces in a large zipper-top plastic bag or bowl with a tight-fitting lid. Pour half of the sauce over the chicken, making sure all pieces are evenly covered. Refrigerate, covered, for 2 to 24 hours.

Reserve the remaining half of the sauce separately.

In a bowl, whisk together 2 tablespoons balsamic vinegar and 2 tablespoons oil. Add portobello slices and toss to combine. Set aside mixture for at least 15 minutes so mushrooms can marinate.

Prepare a gas or charcoal grill for direct heat grilling. While grill is heating, bring reserved half of the sauce to a boil, then reduce heat. Keep warm.

Saute mushroom slices with their marinade in a small saute pan over medium-high heat until soft, about 3 minutes. Keep warm.

Remove the chicken from the marinade. Spray chicken pieces with nonstick cooking spray, making sure to cover them on all sides. Using tongs, wipe the grill grate with a paper towel saturated with vegetable oil. (It is important to oil both the chicken and the grill because the honey makes the marinade especially prone to sticking.)

Grill the chicken just until cooked through, 3 to 4 minutes per side. Serve hot, topped with warmed sauce and sauteed mushrooms.