Preheat oven to 400°F. Place radicchio on a parchment lined baking sheet. Toss with olive oil, sea salt, black pepper, and vinegar. Cook for 15 minutes, until the radicchio has wilted and caramelized.
Heat a skillet over medium heat.
While the skillet is heating, lay 4 slices of bread out on a surface and begin to layer the sandwiches. I like to start with the brie, dividing an equal amount between the bread slices. Next, add the persimmon and radicchio, topped off with another slice of bread.
Liberally butter the bread and place buttered-side down in the skillet.
While cooking on the first side, butter the top slice of bread. Cook for 3-4 minutes, until the bread is crisp and golden brown. Turn and cook until the brie is melted and the bread is golden brown.