Homemade kashk

Step 1: Put the 4 ⅜ lb full-fat plain yoghurt and half the 1 litre ice-cold water in a stand mixer or large food processor and churn on medium for 10–15 minutes, adding the rest of the water halfway, until flecks of butter float to the top.

Step 2: Skim off the butter with a slotted spoon (keep it for cooking if you like). What is left is a thin, sour doogh.

Step 3: Pour the doogh into a heavy pan and heat it over a low heat, stirring gently along the bottom, until it steams and small curds appear, about 20 minutes. Do not let it boil hard.

Step 4: Keep it just below a simmer for 20–30 minutes more, stirring now and then, until the curds clump into soft white lumps and the whey is clear and yellow-green.

Step 5: Line a sieve with a double layer of clean muslin, pour in the curds, then tie up the cloth and hang it over a bowl in the fridge for 12 hours until thick and pasty.

Step 6: Mix the drained curd with the 2 tsp salt. For liquid kashk, blend it with the ½ cup hot water until smooth and creamy, simmer 5 minutes over a low heat in a small pan, cool and spoon into a sterilised jar.

Step 7: For dried kashk, roll the salted curd into walnut-sized balls with damp hands and dry them on a rack in strong sun for 4–5 days or in a 122°F oven for 8–10 hours, until rock-hard right through.

Step 8: Liquid kashk keeps 1 week in the fridge; dried balls keep 6 months in an airtight jar somewhere cool and dry. To use dried kashk, soak and rub it in warm water until creamy. Always heat kashk to a simmer before serving. Throw it away if you see mould, if it smells rotten rather than sour, or if it fizzes.