Hi i tried a cheese sauce for cauliflower cheese bake the other nyt, and it was a flop, apparently you cant really cook quark as it separates you can only gently heat it, i tried adding milk, a bit of corn flour, some mustard and some grated cheese, works out almost synfree if using milk as an HEXA, i heated it till the cheese melted poured it over parboiled veg, sprinkled cheese on top and baked for about 20 mins, and it was foul it had completely separated!
However i then went on to make another cheese sauce that did not separate, i used 600ml skimmed milk, 60g plain flour, 120g grated parmesan, a tsp of mustard and some pepper, stirred continuously on hob till it thickened, then used it for lasagne, it was absolutely divine! it workes out as 6 HEXA's and 10.5 syns for the whole thing, but the lasagne was divided into 6 portions so works out as 1 HEXA and almost 2 syns per serving!
moral of the story dont waste your time with quark making a cheese sauce!