Directions

1. Preheat the oven to 350°F. Line a large baking sheet with parchment paper.
2. Brush the tomato slices with the oil and arrange them in a single layer on the baking sheet. Season with salt and pepper. Roast the tomatoes until they are very soft and just hold their shape, about 1 hour. Remove from the oven.
3. Meanwhile, combine the vinegar and sugar in an 3 qt. saucepan. Bring the mixture to a simmer over medium heat, stirring occasionally. Simmer until the liquid is reduced to a syrupy consistency, about 10-12 minutes.
4. Place 4 slices of the bread on a work surface. Top each with 2 ounces of the mozzarella. Place 2 tomato slices on top, then 4 basil leaves, followed by 2 slices of provolone cheese. Place the remaining slice of bread on each sandwich.
5. Spread the outside of each sandwich with 2 teaspoons of the butter. Heat a large skillet over medium heat. Add 2 sandwiches, cover the pan with a lid or large piece of aluminum foil. Cook until the sandwiches are golden brown and the cheese has melted, about 3-4 minutes per side. Repeat with the remaining sandwiches. To serve, cut each sandwich in half diagonally and drizzle with balsamic syrup.