Step 1: Prepare the Mozzarella - Slice the fresh mozzarella into rounds approximately ¼ inch thick. Arrange the slices on paper towels and gently pat the tops dry.

Step 2: Prepare the Tomatoes - Slice the tomatoes into rounds of similar thickness. Place them on paper towels and sprinkle lightly with salt. Allow the tomatoes to rest for approximately 5 minutes, then pat them dry.

Step 3: Butter the Bread - Spread softened butter across one side of every bread slice. Make sure the butter reaches the edges.

Step 4: Add the First Cheese Layer - Arrange mozzarella slices over the unbuttered side of each bottom slice of bread.

Step 5: Add the Tomatoes - Place the tomato slices over the mozzarella. Season lightly with freshly ground black pepper.

Step 6: Add the Basil - Arrange fresh basil leaves over the tomatoes.

Step 7: Add the Balsamic Glaze - Drizzle approximately two teaspoons of balsamic glaze over each sandwich.

Step 8: Add More Mozzarella - Place another layer of mozzarella over the basil.

Step 9: Close the Sandwiches - Place the remaining bread slices over the filling with the buttered sides facing outward.

Step 10: Heat the Skillet - Place a large cast-iron or nonstick skillet over medium-low heat.

Step 11: Grill the First Side - Place one or two sandwiches in the skillet, depending on its size. Cook for approximately 3–5 minutes.

Step 12: Flip the Sandwiches - Carefully turn each sandwich over with a wide spatula. Cook the second side for another 3–5 minutes.

Step 13: Rest - Transfer the grilled sandwiches to a cutting board. Allow them to rest for approximately 2 minutes.

Step 14: Serve - Cut each sandwich in half with a sharp serrated knife. Drizzle with additional balsamic glaze and garnish with fresh basil if desired.