Start by thoroughly cleaning the lettuce. Remove the butt end and placr lettuce in a large bowl of ice water. Let sit for 5-10 minutes. The dirt will sink to the bottom of the bowl. Take out and pat dry with a clean towel. Cut into bite size pieces. Place in a bowl and cover with a paper towel. Refigerate until the meal is ready to serve.
Preheat oven to 375 and line a sheet pan with foil and parchment paper. Cover the entire pan with foil and wrap foil around the edges. Lay a piece of parchment along the inside to prevent sticking.
Process your vegetables and lay them in the sheet pan. Leave space down the center for your pepper and chicken. I begin with the onion because it doesn’t need to be washed. Peel and slice into 1/4” slices.
Wash the Brussels sprouts and remove the ends and any damaged leaves. Cut in half or quarters if they are very large.
Rinse the eggplant and cut half o it into 1” cubes.
Wipe the mushrooms with a damp paper towel. Remove the stems and cut into 1/4” strips.
Wash the red bell pepper. Remove the stem, seeds, and ribs. Slice into 1/4” slices. Lay the pepper down the center of the pan to act as a makeshift grill pan.
Rinse your parsley leaves and pat dry. Roll the leaves into a tight ball on the cutting board and work the knife through the bundle back and forth until you have a fine mince. Peel and mince garlic. In a small bowl mix parsley, garlic, balsamic vinegar, olive oil, and spices together.
Remove chicken from package and lay it on top of the red bell pepper strips.
Drizzle 2/3rds of the marinade over the top of the chicken and vegetables. Using your hand or tongs gently toss the vegetables and chicken to get an even coating of marinade all around.
Place in preheated oven for 20 minutes. After 20 minutes turn the broiler on low and let the chicken brown for 3-5 minutes. This will help the sugars in the balsamic to turn into a glaze.
Remove the sheet pan from the oven. Serve chicken and vegetables atop crisped lettuce dressed with the remainder of the marinade/dressing.