Combine first 5 ingredients. Divide ground chuck into 4 equal ¼ lb patties. Brush portabella caps with extra virgin olive oil and salt and pepper both sides. Preheat grill. Grill mushrooms for about 6 minutes on each side or until soft. Grill burgers until desired doneness. The last minute of grilling, place cheese on burgers. Layer 1 mushroom cap, mayo, lettuce, add a little salt and pepper on tomato, onion, dill pickle, 2 cheeseburger, and top off with mushroom cap. For a lower fat version, use ground turkey and low fat cheese.