01 - In a small saucepan over medium heat, combine balsamic vinegar and honey. Simmer gently for 3 to 5 minutes until slightly thickened. Remove from heat and allow to cool briefly.
02 - Spread softened butter on one side of each bread slice. Arrange two slices, buttered side down, on a clean work surface.
03 - Evenly layer brie slices over the bread, sprinkle with shredded cheddar, and top with blackberry halves. Drizzle each with about 1 teaspoon of the prepared balsamic glaze.
04 - Cover with the remaining bread slices, buttered side facing up.
05 - Heat a nonstick skillet or griddle over medium heat. Place the sandwiches in the pan and cook for 3 to 4 minutes per side, pressing gently, until the bread is golden and cheese is melted.
06 - Remove sandwiches from the pan. Let rest for 1 minute, then slice and serve warm.