Preheat a croustade iron in oil for at least 30 minutes (150-160C).
Mix all dry ingredients.
Combine beer, cheese water and egg and whisk the liquid into the dry mixture.
Add the melted butter and let it swell for a few minutes before you start frying.
Pour the batter into a container that is preferably taller than it is wide because you need to dip the iron (for example, a coffee cup).
When you take the iron out of the oil, it's a good idea to wipe off any excess oil with a terry towel (you want it to be thick so you don't burn yourself) before you dip the iron into the batter - this will help the batter stick better and not slip off/create holes as easily.
Let the batter fry until golden brown - about 1 minute, but it depends a lot on the temperature of the oil.
When the croustade is ready, remove the iron from the oil and carefully pry the crust off the iron with a fork onto a sheet lined with paper towels.
Once the croustades have cooled, you can store them in an airtight container for about 2 months.