What could I substitute for coffee in an Opéra cake I would like to bake an Opéra cake for someone who doesn't really appreciate the taste of coffee. Since coffee and chocolate are the two main elements, I am wondering: what flavour could I substitute for coffee in my coffee buttercream? I suppose the qualities I'm looking for are a bit of bitterness, and it should go well with chocolate and orange liquor?



PS: I just noticed that the English wikipedia describes the sponge cake as “soaked with coffee”, but in the way I usually do it it's soaked with Cointreau so I don't need any replacement there.
Some sort of nutty flavor perhaps? Hazelnut syrup? I think it should go well with both chocolate and orange. Otherwise I think the cake will be quite delicious even without a substitute, just using plain buttercream. 

EDIT: I just noticed that the cake has an almond base. Perhaps a few drops of Amaretto in the buttercream would work. That would play nicely with the almond flavor already there.