Quark is not easily available in most non German countries, and it cannot really substituted by ricotta or creamcheese. But then it's not really difficult to make. This is the way we made it at my friend's house in a tiny village in the Black Forest where I spent my summer vacations when I was 13. 1 litre (1 1/8 quart) milk makes about 300 - 350 g (ca. 8 - 12 ounces) quark.
- Fill the milk into a bowl, stir in the lemon juice and let stand on the kitchen counter overnight, about 16 hours.
- After 16 hours, it should have turned into soured milk.
- Slowly heat the soured milk to no more than 122° F (50° C) until the whey starts to seperate from the solids.
- Let cool and pour into a sieve lined with a cheesecloth.
- Let drip for 12 hours, then press out any remaining liquid and strain the quark through a sive (it get smoother then).