How to Make It
Preheat oven to 350°F. Using a serrated knife, make lengthwise cuts 1 inch apart in bread loaf, cutting to but not through the opposite side. Make crosswise cuts 1 inch apart in loaf, cutting to but not through the opposite side, creating “cubes” in loaf. Set aside.
Toss together Cheddar, mozzarella, and basil in a medium bowl; set aside.
Melt butter in a small saucepan over medium. Add garlic, and cook, stirring often, until fragrant, about 1 minute. Add soup and pepper; cook, stirring occasionally, until heated through, 2 to 3 minutes. Carefully pour soup mixture evenly into cuts in bread loaf. Stuff cheese mixture into cuts in loaf.
Transfer stuffed bread loaf to a baking sheet; let stand 15 minutes. Cover bread loaf loosely with aluminum foil. Bake in preheated oven until golden and bubbly, about 25 minutes. Serve immediately.