Who doesn't want to try a bite of a sandwich dripping with blueberry sauce and Gruyere cheese? It's easy to get past the strange sounding combination when your dinner looks like this!
Toss blueberries with sugar in small saucepan and cook over medium-high heat, mashing occasionally with a fork, until slightly thickened, about 5 minutes. Set aside.
Evenly top 2 bread slices blueberry mixture and cheese slices. Top with remaining 2 bread slices.
TIP: For perfectly crispy results, spread outside of sandwiches evenly with Hellmann's Real Mayonnaise.
Cook sandwiches in large nonstick skillet over medium heat, turning once, until golden brown and cheese is melted, about 5 minutes.