In a large cast iron skillet, melt the butter over medium high heat and add the sourdought cubes, stirring to coat well.
Lower the heat to medium and continue cooking the bread, stirring often, until the croutons start to brown slightly and form a crust on the edges. Add the Parmesan and garlic powder.
Cook for an additional few minutes until the croutons are lightly browned. Turn off the heat and let the croutons cool fully in the pan. They will get crunchier as they cool! Store the croutons in an airtight container for up to one week.
