01 - In a small mixing bowl, gently combine blueberries, honey, and lemon zest if using.
02 - Generously spread cream cheese on one side of each bread slice.
03 - Evenly sprinkle shredded mozzarella cheese over half of the cream cheese–coated bread slices.
04 - Spoon the berry mixture onto the mozzarella-covered bread, ensuring an even distribution.
05 - Top each with the remaining bread slices, cream cheese side facing in, to create sandwiches.
06 - Spread softened butter smoothly on the outside of each sandwich.
07 - Preheat a nonstick skillet over medium heat. Cook sandwiches for 3 to 4 minutes per side, gently pressing until golden brown and cheese is fully melted.
08 - Transfer sandwiches to a board, let cool briefly, slice in half, and serve immediately while warm.