1. Combine first 4 ingredients in a bowl. Spread filling on 4 bread slices; top with remaining bread slices.
2. Heat a large nonstick skillet over medium-high heat. Coat tops of sandwiches with cooking spray. Arrange sandwiches, top side down, in pan. Coat sandwiches with cooking spray. Cook 2 to 3 minutes on each side or until cheese melts and bread is golden brown.