Add the grated cheeses, butter, flour, salt, onion powder, and garlic powder to a food processor.
Pulse until the mixture looks crumbly and evenly combined.
With the processor running, add the cold water a little at a time until the dough just comes together.
Tip the dough out, press into a disc, wrap in cling film, and refrigerate for 30 minutes.
Preheat the oven to 190°C fan bake and line a baking tray with baking paper.
Roll the dough out very thin on a lightly floured bench.
Cut into small squares and place on the tray. Prick each cracker with a fork.
Bake for 12–15 minutes, until golden and crisp.
Cool completely on a rack before storing.