How to swap Greek yogurt for sour cream, cream, butter, mayonnaise and buttermilk; why it tenderises meat; how to keep it from splitting in a hot pan; and a Greek yogurt cake that works every time.

One litre of milk, a spoon of live yogurt, a cloth and about 12 hours. The method, the temperatures that matter, what to do with the whey, and why your batch came out thin.

The two bacteria, the temperatures, the straining methods (cloth bag, separator, ultrafiltration), the 3-to-1 milk ratio and what happens to the whey.