Place the parmesan cheese in the bowl of a food processor and blend until fine. Alternatively, if making this by hand simply grate the cheese on the fine side of a box grater.
Add the butter, flour, garlic powder and salt and blend until the dough forms a ball in the food processor.
Transfer the dough to a sheet of parchment paper and roll into a log.
Roll in the parchment paper, making sure the dough is completely covered, then twist the edges to secure.
Place in the fridge for at least 2 hours to firm up.
Once chilled, slice the dough into ½cm slices and place on a baking sheet lined with parchment paper. Space the discs at least 5cm apart.
The crackers are best baked from chilled so only slice them right before baking OR return them to the fridge once sliced while you preheat the oven.
At this stage you can also freeze the discs to bake later (from frozen): Allow them to freeze in a single layer then transfer to a freezer bag and keep for up to 3 months in the freezer.
Once you're ready to bake, preheat the oven to 180°C/350℉.
Place the crackers in the oven and bake for 10-12 minutes until golden around the edges.
Remove from the oven and allow to cool for 5 minutes then transfer to a wire rack and allow to cool completely.
Store the crackers in an airtight container for up to 7 days.