Scrape the portobello mushrooms clean, and slice them lengthwise, about a 1/4-inch thick. Season the chicken breast with salt and pepper. Heat 1/2-ounce of olive oil in a heavy saute pan, over high heat. Saute chicken breasts until firmly cooked through and browned on each side, approximately 3 to 4 minutes. Remove from the pan, add the sliced onions, add 1/2-ounce more olive oil if necessary, saute until brown and caramelized, scraping all the chicken bits from the pan. Add the mushrooms and continue sauteing until they are soft, another two minutes. Add thyme, grapes and de-glaze the entire pan with green verjus or white wine. Reduce the liquid until it is almost dry, then swirl in butter. Thinly slice the chicken. On one slice of bread, arrange one chicken breast and top with the onion and portobello mixture. Top with other slice of bread. Repeat with second sandwich.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of Exec. Chef John Villa,Park View at the Boathouse, New York, NY