Shred the block of cheddar cheese and mix with the flour until evenly coated.
Heat the cast iron fondue pot on the stove at a medium, then add in the beer. Bring to a light boil then add in the garlic, Worcestershire, and mustard powder and stir.
Gradually add the cheese into the liquid, stirring constantly. Reduce the heat to low and continue to stir until it comes together and melts. If the liquid seems split from the cheese just continue to stir until it combines.
Transfer to the fondue pot stand, light the Sterno to keep the cheese warm and serve!
