Quark

Quark is a German whole or skimmed milk (or low fat) cheese made without rennet. The word quark means "curd". It's similar to a cross between a thick, strained yogurt and a fromage blanc. It is a good low fat replacement for butter in scrambled eggs or in mashed potatoes. It can be used to make cheesecake, spread on bread or served with fresh fruit.

Quark can be purchased plain or, like yogurt, blended with fruit.

Substitutions for quark include equal amounts of:
Fromage frais or fromage blanc
OR Mascarpone cheese (richer)
OR 2 parts ricotta and 1 part sour cream