Curd cheese
Fresh cheese made from soured milk, mildly tangy; in Hungarian cooking, as túró, it is usually dry and crumbly rather than creamy.
In German-speaking countries quark is sold in every supermarket; for Hungarian recipes the low-fat kind, well drained, or crumbly layered curd cheese works best. In English-speaking countries it can be found in larger supermarkets, Eastern European shops, or sold as farmer's cheese.
Substitute:
Cottage cheese pushed through a sieve and drained overnight comes closest to the crumbly texture; drained ricotta also works but tastes sweeter and less tangy.