Preheat the broiler.
Brush the bread on both sides generously with oil and place on a baking sheet. Broil until golden and crispy, 2 minutes per side.
Remove, let cool slightly, and rub the garlic all over one side of each slice. Place a slice of cheese on each piece of bread, then top each with a slice of prosciutto. Return to the oven until the cheese is melted and golden, 2 minutes.
Garnish with a basil leaf and serve.
Adapted from "One Dish at a Time: Delicious Recipes and Stories from My Italian-American Childhood and Beyond" by Valerie Bertinelli © Rodale 2012. Provided courtesy of Valerie Bertinelli. All rights reserved.