Combine butter, garlic, garlic powder and salt in a heatproof bowl and melt in the microwave. Stir through parsley.
Cut the bread on a diagonal into 1" diamonds but do not cut all the way through the bread.
Use your fingers or a knife to pry open each crack and drizzle in a teaspoon of butter and stuff in a pinch of cheese. This might sound like a bit of an effort, but I promise you it is worth it! You don't need to be super neat, it's nice to have some of the butter drizzled over the crust.
Brush surface with remaining butter.
Wrap with foil and bake for 20 minutes until the cheese has mostly melted, then unwrap and bake for 5 - 10 minutes more to make the bread nice and crusty.
Serve immediately. (See note 1 for best make ahead methods)