FRESH BASIL PESTO
Combine the basil, garlic and pine nuts in a food processor and pulse until coarsely chopped. Slowly add the olive oil through the processor chute with the machine running. Process until fully incorporated and smooth. Empty into a mixing bowl and stir in the Pecorino cheese. Season to taste and reserve.
Pour the balsamic vinegar into a shallow container and add the tomato slices in a single layer. Turn to coat both sides with the vinegar. Lightly season with salt and pepper, cover with a layer of plastic wrap and press down gently to cover. Chill in the refrigerator for a minimum of 30 minutes (up to 2 hours).
FINISHING THE DISH
Divide the sliced tomatoes and sliced fresh mozzarella into four equal portions. Place one slice of marinated tomato on a service plate. Overlap with a slice of fresh mozzarella. Repeat in this pattern until all tomato and mozzarella slices for the first serving are exhausted. Repeat with the remaining servings. Drizzle extra virgin olive oil over the top of each serving (if desired) and garnish with the chiffonade of basil.