1. Prepare grill.
2. Coat both sides of mushroom caps with cooking spray. Place mushroom caps, gill side down, on grill rack coated with cooking spray. Grill 5 minutes; turn mushrooms over, and top evenly with cheeses. Grill 5 minutes or until cheeses melt.
3. Spread 2 1/2 tablespoons Smoky Red Pepper Mayo evenly on cut sides of each sandwich thin. Place a mushroom cap, cheese side up, on bottom of each sandwich thin. Top with sandwich thin tops.
Round sandwich thins are a tasty alternative to regular sliced bread. Each serving contains 100 calories and 5 grams of fiber, which is comparable to a single slice of bread.