Coat mushrooms with oil, salt and pepper. Saute mushroom caps for 12 minutes, then remove from pan (may also be cooked on pre-heated grill.) Add bay shrimp, crabmeat, garlic, green onion, diced tomato, parsley, salt and pepper. When shrimp are almost done, add white wine, lemon juice, cream and reduce down. Finish sauce with whole butter and leaf spinach. Cut Portabello mushroom in quarters and top with crabmeat and shrimp butter sauce.