1. In a small bowl, stir together olives and oil.
2. Place a slice of tomato on each of 4 small plates; sprinkle lightly with salt and pepper. Top each with a slice of mozzarella, then a basil leaf. Repeat layering one more time. Top each stack with a slice of tomato and garnish with basil leaves.
3. Drizzle olive dressing over each stack. Serve immediately.