Preheat oven to 400 F. In a baking dish, combine cooking wine, olive oil, soy sauce, balsamic vinegar, and garlic. Place mushrooms in the baking dish (stem side up) and spoon some marinade into each mushroom. Set aside for about 20 minutes.
While the mushrooms are marinating, make the dressing. Combine mustard, vegetable oil, red wine vinegar, and maple syrup and whisk until smooth and creamy. Set aside.
Cover baking dish with foil and bake for 30 minutes. Remove the foil, flip the mushrooms, and bake for another 10 minutes. Cool for ten minutes, then slice thinly.
Mix greens, avocado, onion and chickpeas in a large bowl. Add dressing and toss. To serve, place a generous helping of salad on each plate. Top greens with sliced portabello.
Recipe by Baked In at https://www.baked-in.com/2012/04/28/portabello-salad-with-maple-mustard-dressing/