Preheat oven to 375 degrees F and preheat a cookie sheet in it.
Melt the butter in a large skillet over medium heat and cook until it foams. Add the garlic and cook until fragrant, about 30 seconds to 1 minute. Add the bread cubes and toss to coat with the butter. Season with salt and pepper. Transfer the bread to a baking sheet. Immediately sprinkle with the cheese and toss again while warm to melt the cheese.
Bake, stirring once or twice, until the croutons are crisp and lightly colored on the outside but still soft within, about 8 or 9 minutes. Let cool. Store in an airtight container.
Michael's Notes: I use a serrated knife to remove the crust from day-old bread, then switch to a chef's knife to cut the cubes because it doesn't tear the bread. Also note that I recommend grating the Parmesan finely so that it will stick to the bread better.