What is
Clabber is a food produced by allowing unpasteurized milk to turn sour at a specific humidity and temperature. Over time, the milk thickens or curdles into a yogurt-like substance with a strong, sour flavor.
Quark is a type of fresh dairy product, common for the cuisines of German-speaking countries made by warming soured milk until the desired degree of coagulation (denaturation, curdling) of milk proteins is met, and then strained.