Preheat oven to 210 C (410 F) and line a baking tray with baking paper.
Whisk egg and flour together until smooth.
Add mustard and grated cheese, mix to combine.
Drop tablespoon sized amounts onto the prepared baking tray, evenly spaced.
Bake for 10-12 minutes, or until golden brown.
Makes approximately 20.
These can be enjoyed warm or cold, but allow them to cool before storing them in an airtight container in the fridge. Will last in the fridge for up to a week. Freeze in an airtight container, separate layers with baking paper.