I laid out a large square of foil and sprayed it with cooking spray, then laid a boneless, skinless chicken breast on it. I spread the chicken breast with a crushed clove of garlic, then seasoned with salt, pepper, and Essence of Emeril. I topped the chicken with 4-5 thin slices of red onion and about 4-5 sliced mushrooms. On top of that I put about a tablespoon of butter, then about 1/4 cup of sauce.
The sauce I made with about 1/4 cup canola oil, about 1/3 cup balsamic vinegar, about 1/3 cup lemon juice, and about a teaspoon each of red pepper flakes and dried thyme. Fresh would have been better, but my thyme plant died last month.
I planned to grill the packets for about 20 minutes on a covered grill on medium heat, but a thunderstorm was coming through the area at the time, so I did end up using my oven. I cooked the packets at 400F for about 25 minutes.