Heat Skillet, butter your slices of bread. Layer your sandwich with 1 Tbsp. Pesto, 1 oz. of Mozzarella Cheese, 3 slices of tomatoes, about 1/2 Tbsp. of Balsamic Vinegar, another oz. of Mozzarella and if you want you can add an extra Tbsp. of Pesto. Close with top piece of bread and allow to cook for 4-5 minutes each side until golden brown.