Caprese Grilled Cheese Sandwich with Balsamic Basil Mayo

Preheat griddle or stove top pan to medium-low to medium heat. In a small bowl, combine mayo, basil and balsamic vinegar. (Add more or less basil or balsamic vinegar to your taste). Evenly spread butter on one side of a slice of bread. Place this side down on the griddle or pan. Quickly spread the balsamic mayo on the side of the bread facing up, then quickly assemble your sandwich with the mozarella and tomatoes. Sprinkle with a dash of salt and pepper. Evenly spread butter on one side of the other slice of bread. Place on top of the sandwich with the buttered side up. Cook for about 3 minutes on each side, until cheese is melted and bread is golden brown.