Preheat oven to 375 degrees F. Prepare a large piece of aluminum foil; set aside.
Mix together butter, garlic powder, salt, parsley, and half the Parmesan. Make deep, even cuts into bread, about 1/2 inch apart, without cutting through bottom. Spread butter mixture inside each slice; spread remaining butter on the outside of the loaf.
Place bread on top of aluminum foil. Top with remaining grated Parmesan. Gather up sides of aluminum foil to make a packet for the loaf, leaving a small slit at the top.
Bake for 10-15 minutes, or until the top is crisp and inside is soft and fluffy.