Preheat the oven to 300 degrees F (150 degrees C).

Mix butter, Parmesan, garlic salt, rosemary, basil, thyme, and garlic powder together in a small bowl. Spread 1/2 of the mixture onto each piece of French bread. Sprinkle with additional Parmesan cheese if desired. Transfer bread, seasoned-side up, to a medium baking sheet.

Bake in the preheated oven until the edges are very lightly browned, 10 to 12 minutes.