Char peppers directly over gas flame, on grill, or under broiler until blackened on all sides. Place peppers in a metal bowl and cover with plastic wrap; let stand 10 minutes, then peel.

Set a strainer over bowl. Holding peppers over bowl to catch juices, remove and discard seeds and ribs. Cut peppers into thin strips and add to bowl with reserved juices. (If you want to prepare peppers a day ahead, just cover and refrigerate; bring to room temperature before using.)

Add basil and minced garlic to peppers and set aside. Preheat broiler. Arrange bread slices on a baking sheet. Broil until toasted, about 2 minutes. Turn bread slices over and brush them with oil. Broil until golden, about 2 minutes. Rub each bread slice with whole garlic cloves. Top with a spoonful of pepper mixture. Season to taste with salt and pepper.