Slice chicken breasts in half horizontally, and place into a zip top bag and add marinade. The chicken should marinate for at least 30 minutes, it is better if you allow it to marinate longer. I like to let mine marinate overnight when possible.
Heat a large skillet to medium heat. Add a vegetable oil. When the vegetable oil heats up add chicken. Cook the chicken for 6 to 7 minutes on one side, then flip over and cook on the other side for 4 to 5 minutes. The chicken should have a lightly browned outside edge.
While the chicken is cooking toss together the cheeses (Gruyere, white Cheddar, Parmesan, and Fontina). If you desire to make the cheese sauce by heating together the heavy cream and 1/2 cup of the cheese in a small skillet over low heat. Also, add the Panko breadcrumbs to a small bowl and add the melted butter. Toss the Panko breadcrumbs with the melted butter until they are lightly coated with butter.
Set your oven to broil. To assemble the chicken place chicken on an oven safe dish or pan and add about 1 tablespoon of cheese sauce to the chicken, then add shredded cheese blend, then top with buttered Panko Bread Crumbs. Do this for each of the chicken breasts. Place the chicken under the broiler and broil for 3 to 4 minutes or until the cheese begins to brown.