Once you've mastered the jam roll, there are a multitude of variations - and this is one of my favourites. The blueberry roll is light, refreshing, visually stunning and absolutely delicious. About Quark: A German dairy product somewhere between fromage frais and fromage frais spread, Quark is creamy, dense and widely used in desserts. It is easily found in supermarkets or cheese shops. → Can be replaced by well-drained Greek yoghurt if required.