Drizzle cut sides of muffin halves evenly with 1 tablespoon olive oil. Broil 5 1/2 inches from heat (with electric oven door partially opened) until lightly toasted; let cool.
Spread 1 1/2 teaspoons pesto over each muffin half; sprinkle each with 1 tablespoon minced olives. Top each muffin half with 1 piece of mozzarella cheese and 2 tomato slices.
Sprinkle muffin halves evenly with salt and pepper. Drizzle remaining 1 tablespoon olive oil evenly over muffin halves. Bake at 400° for 8 minutes or just until cheese melts and crostini are thoroughly heated.