01 - In a small bowl, gently combine fresh blueberries with honey and lemon zest, if using.
02 - Evenly coat one side of each bread slice with softened cream cheese.
03 - Distribute shredded mozzarella cheese over half of the bread slices on top of the cream cheese layer.
04 - Spoon the blueberry mixture evenly over the mozzarella cheese.
05 - Close with remaining bread slices, cream cheese side facing inwards, to form sandwiches.
06 - Spread softened butter over the outer sides of each sandwich.
07 - Heat a nonstick skillet over medium heat. Place sandwiches in the skillet and cook for 3 to 4 minutes per side, pressing gently, until golden brown and cheese is melted.
08 - Remove sandwiches from the skillet, allow to cool briefly, slice in half, and serve immediately while warm.