In a small bowl, mash the blackberries with a fork. Stir in the honey, thyme, salt, and black pepper.
Spread ½ tablespoon of butter on both sides of each bread slice. Layer one buttered slice of bread with one slice of brie, a spoonful of blackberry sauce, prosciutto, and another slice of brie. Cover the stack with another slice of buttered bread.
Melt 1 tablespoon butter in a large skillet over medium heat. Add the prepared sandwiches and press down until cheese starts to melt and the bread turns golden brown on each side, approximately 3-4 minutes per side.
Serve immediately with remaining blackberry sauce for dipping. Enjoy!
