Brush one side of each bread slice equally with butter. Place bread on a work surface, butter side down. Spread 4 bread slices equally with chocolate-hazelnut spread, Top with Brie and raspberries, Cover with remaining bread slices, butter side up, and press together gently.
Place sandwiches on preheated panini grill or in a large skillet over medium heat and cook, turning once if using a skillet, for 3 to 4 minutes or until golden brown and cheese is melted. Serve immediately.