I want to make Heston's Chocolate Truffle recipe, which calls for using double cream. But, I'm living in Oslo, Norway and the only cream I can find is called "fløte", which as far as I can tell, is just whipping cream with 38% fat.

Does anyone know of a suitable and obtainable substitute for double cream, or an effective way to thicken whipping cream enough for it to work in this recipe?

I've read some suggestions elsewhere to use Crème fraîche, but I think that would be a bit sour for this particular recipe.

Alternatively, could I, for example, reduce the whipping cream by simmering it on a low heat till it thickens, or perhaps thicken it with xanthan gum, agar agar, gelatine, butter or something, without ruining it?