Cut the bread lengthwise and then widthwise without cutting into the bottom of the bread.
Place on a parchment lined baking sheet. Place the cheese slices between the cuts of bread. Really fill in the bread with as much cheese as you can fit.
Combine butter, green onions, garlic powder, and Parmesan cheese. Pour evenly over the bread.
Cover the bread with foil and bake for 15 minutes. Uncover the bread and bake for 10 minutes longer. Serve hot.