Preheat the oven to 350 degrees F. Melt 3 tablespoons butter with 1 teaspoon truffle oil in an ovenproof skillet over medium heat. Add 2 slices bread, and toast on both sides. Set the toast aside and reserve the skillet.
Lay out one slice of untoasted bread. Top with one-quarter each of the brie, figs and jack cheese, then a slice of toasted bread, then another layer of brie, figs and jack. Close with a slice of untoasted bread. Repeat to make another double-decker sandwich.
Melt the remaining 3 tablespoons butter with the remaining 1 to 2 teaspoons truffle oil in the skillet over medium heat. Add the sandwiches and cook until golden on the bottom, about 3 minutes. Flip and cook until golden on the other side, about 2 more minutes, then transfer the skillet to the oven and cook until the cheese is melted, 6 to 8 minutes. Serve with the fig preserves.