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