Inspiration from [Yammie’s Noshery|http://www.yammiesnoshery.com/2012/02/caprese-grilled-cheese.html]
Heat a frying pan or flat griddle pan to medium-low. Brush olive oil onto one side of each slice of sourdough bread.
On a cutting board or other work surface, assemble sandwich: bread (dry side up), mozzarella, tomato, basil leaves, sea salt, mozzarella, bread (dry side down) - being generous with all the ingredients.
Carefully place sandwiches in hot pan and cook on oiled side until golden and crispy. Flip and repeat.
Take garlic half and rub on the browned side of each slice of bread. Sprinkle with sea salt. Slice on the bias and serve hot.