Kefir

Kefir grains are soft clusters of bacteria and yeasts that ferment milk; despite the name, they are not made from wheat or other cereals. They can be strained out and used to start another batch.

Stir kefir grains into pasteurised milk in a clean jar, cover it loosely and leave it at room temperature until tangy and slightly thick, usually about 18–24 hours. Strain out the grains and refrigerate the kefir.

Keep kefir covered in the fridge and use it within about a week for the freshest flavour. A little separation is normal; stir or shake it gently before serving.

Kefir can split if boiled, so stir it into soups or sauces after taking them off the heat. It also works well in pancake batter, where gentle cooking prevents the batter from tasting overly tangy.

Blend it with berries and banana for a smoothie, or pour it over oats with fruit and nuts. Its tartness also suits cucumber, garlic and herbs in a quick salad dressing.

Use plain kefir in place of buttermilk in pancakes, scones or marinades, measure for measure. It is thinner than most yoghurt, so drain it through a clean cloth first if you need a thicker substitute.

For a more reliable home fermentation, start with pasteurised milk and clean equipment; raw milk can carry harmful germs that fermentation may not eliminate. Keep the finished kefir chilled.