I found this recipe in Simple Foods for the Pack by Axcell, Kath, Cooke. It sounds wonderful. Simpler than a regular fondue with cheddar and beer rather than emmentaler, gruyere and wine.
8oz grated cheddar cheese
2 Tablespoons cornstarch
1/2 teaspoon dry mustard
1 cup beer, preferably ale
1-2 cloves garlic, crushed in camp
At home: Package cheese in a Ziploc plastic bag. Combine the cornstarch and mustard in a separate bag. Carry beer and garlic separately.
In camp: Place beer, cheese and garlic in a thick bottomed pan or use a heat diffuser. Cook over low heat, stirring constantly, until the cheese has melted. Blend cornstarch and mustard with a little extra beer or water. Add to the fondue and stir until thickened. To eat, dip chunks of bread, skewered on a fork or chopstick. You can use a double boiler setup to keep it warm while eating it.
From Simple Foods for the Pack, third edition by Axcell, Kath and Cooke