Preheat oven to 400F (200C). Place basil, garlic, oil, salt and
pepper in a blender. Whirl to a saucy consistency. Add more oil to
make it more saucy, if needed. If making ahead, cover and
refrigerate up to 2 days. Cut bread in half horizontally, then cut
each half into quarters. Place cut side up on a rimmed baking
sheet. Spread half of basil mixture over bread, then evenly sprinkle
with mozzarella. Thickly slice bocconcini and tomatoes into
rounds, then arrange in overlapping slices on top of bread.
Sprinkle with more salt and pepper. Bake in centre of preheated
oven until cheese starts to melt, 7 to 10 minutes, then turn broiler
to high. Broil until cheese begins to turn golden, 5 to 10 minutes.
Remove from oven and drizzle with remaining basil mixture. Cut
each piece in half diagonally. Best served warm.