Making fondue tends to be a tricky, fussy project requiring specialty pots and chafing dishes and incessant stirring to help the cheese melt evenly and stay molten. We wanted to take advantage of the heat-retaining powers of cast iron to make a beer and cheddar fondue that would stay creamy without constant attention.
A combination of mild cheddar and highly meltable American cheese provided a nice creamy base, but it turned grainy when combined with the acidic beer. To stabilize it, we added cornstarch, which acted as an emulsifier, plus garlic and dry mustard to complement the flavor of the cheddar.
This dip is served right in the skillet; the residual heat of the cast iron helps the fondue stay warm and melty. The fondue tasted best when made with block cheese that we shredded ourselves; we recommend that you buy a block of American cheese from the deli counter. Pre-shredded cheese will work, but the fondue will be much thicker. A mild American lager, such as Budweiser, works best here.
For dipping we like to use bread cubes, apple slices, steamed broccoli and cauliflower florets and cured meats. The fondue will stay warm in the skillet for about 15 minutes. To reheat, return the skillet to low heat and cook, stirring constantly, until the fondue is smooth and begins to bubble, 5-10 minutes. Adjust the consistency with warm water, 1 tablespoon at a time, as needed.
Toss cheddar, American cheese, cornstarch, mustard, pepper and cayenne in bowl until well combined.
Bring beer and garlic to boil in 10-inch cast-iron skillet over medium-high heat. Reduce heat to medium-low and slowly whisk in cheese mixture, 1 handful at a time. Continue to cook, whisking constantly, until fondue is smooth and begins to bubble, 4-6 minutes longer. Serve.