Digestive cookies – substitute in South Africa

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.

I would use any uncolored brandy made from distilled fruit. Himbeergeist, sliwowitz, or what you can lay your hands on.

Kirsch doesn't taste much like cherries, and I suspect that it functions more as a solvent for some of the aroma in the spices than for adding its own taste. Even though it does contribute a bit, the taste will be subtle, and other slight fruity notes from a different fruit brandy will blend with the heavy spices just as well.

In a pinch, you could use a colored brandy too, like Chantre. But it will add more of its own flavor, and while it can make a good combination, it will be further from the original than a random obstwasser.

I would avoid any liqueurs, they will add way too much foreign taste, and also won't have enough alcohol to solve the spices in the same way.