01 - In a small saucepan over medium heat, combine balsamic vinegar and honey. Simmer for 3 to 5 minutes until thickened. Remove from heat and set aside to cool slightly.
02 - Spread softened butter on one side of each bread slice. Position two slices, buttered side facing down, on a clean surface.
03 - Arrange brie slices in an even layer on the bread. Sprinkle with shredded cheddar and distribute blackberry halves evenly. Drizzle each with about 1 teaspoon balsamic glaze.
04 - Place the remaining bread slices over the filling, buttered side facing up.
05 - Heat a nonstick skillet or griddle over medium heat. Place assembled sandwiches in the pan and cook 3 to 4 minutes per side, pressing gently until the bread turns golden and the cheese melts.
06 - Remove sandwiches from heat and let rest for 1 minute. Slice as desired and serve promptly while warm.