Toss the sliced or grated cheese with the potato flour or corn flour. Leave until it comes to room temperature. Rub the inside of a fondue pot with the cut garlic.
Start off the fondue on your stove. Pour in the beer and heat until almost boiling. Add a good handful of grated cheese and stir until it melts, moving it about in the pan with a zig-zag motion (stirring it in a circular motion makes the cheese more likely to separate from the liquid.
Gradually add the remaining cheese until you have a smooth, thick mass (this takes about 10 minutes). If it seems too thick, add a little hot water. Add the whiskey, if using, and season with freshly ground pepper.
Place over your fondue burner and serve with small, bite-sized chunks of sourdough or country bread. Use long fondue forks to dip the bread into the fondue.