In a large bowl, toss the arugula with 1 1/2 tablespoons vinegar and 1 tablespoon olive oil; season with salt and pepper. Transfer to a platter.
In the same bowl, toss the tomatoes, mozzarella, onion, basil and mint with the remaining 1 1/2 tablespoons vinegar and 1 tablespoon olive oil; season with salt. Spoon onto the arugula.
