Adjust oven rack to middle position and heat oven to 500 degrees.
Meanwhile, toast garlic cloves in small skillet over medium heat, shaking pan occasionally, until fragrant and color of cloves deepens slightly, about 8 minutes (see illustration at right).
When cool enough to handle, skin and mince cloves (you should have about 3 tablespoons).
Using dinner fork, mash garlic, butter, cheese, and salt in small bowl until thoroughly combined.
Spread cut sides of loaf evenly with butter mixture; season to taste with pepper.
Transfer loaf halves, buttered side up, onto rimmed baking sheet; bake, reversing position of baking sheet in oven from front to back halfway through baking time, until surface of bread is golden brown and toasted, 5 to 10 minutes.
Cut each half into 2-inch slices; serve immediately.