Among the many questions I start getting at work as we near the holidays is: do you sell kirsch? So you’re making fondue. My answer is generally to lead them to the best Gruyere, a bit of cheddar, and some sort of lovely stinky cheese, because truly excellent cheese is more important than any other ingredient in your fondue. It makes up 95% of what’s in your pot, so spend 95% of your time and money on it.
Then when pressed, I admit I really have no idea what kirsch is (other than it must involve cherries) or where to get it. Every time I’ve made fondue I just use beer or white wine.
Kirsch is a cherry brandy, NOT a cherry liqueur. It is generally made with tart, not sweet cherries, and aged in barrels to add a woody flavor. The important lesson in all this is that it is something that adds a tart bite, NOT sweetness. So don’t substitute any old fruity liqueur or maraschino cherry juice if you decide not to buy a whole bottle of this hard to find and esoteric ingredient.
The main reason for adding kirsch is if you are using bland or underripe cheese. The acid is there to enhance the flavor, the same way a bit of lemon juice zips up a boring salad or pasta. If you omit it and just use good ripe or sharp cheese, your fondue will be lovely. If you’d like to add something as a substitute, use an especially tart white wine like a Sancerre or add a splash of a sour beer (I would mix it with a tamer beer like an IPA, unless you find one that’s just a little bit sour. Petrus sounds like a likely candidate to me).
Our friends are having their second annual fondue and bad Christmas movie night this weekend–maybe I’ll try to test the sour beer theory and get back to you.