"This recipe is my variation of one that came with my yogurt maker. It's easy to create Greek yogurt from this, too! Simply strain the yogurt in a colander lined with fine cheesecloth or coffee filters. Using kefir at the start creates a much more tart yogurt from the start; it tastes a lot like Sana from Europe. You can substitute plain yogurt with live active cultures for the kefir, if desired. Save 1/2 cup of yogurt to use a starter, if desired. Eat yogurt within a week."