Brush both sides of the bread with olive oil and then rub with garlic halves. Place one slice flat on a plate and layer with half the cheese, prosciutto, arugula and tomato. Top with remaining cheese and bread.
Heat a skillet over medium. Place the sandwich in the pan and heat until the cheese begins to melt and bread toasts, about 4 minutes per side. Cut the sandwich in half or in quarters and enjoy while warm.