Mix ingredients into dough and leave at room temperature for 24 hours, covered with a piece of cloth. It should become foamy and smell sour and yeasty. Use as indicated in recipe, but leave 50g of starter dough behind for future use.
For every 50g starter dough left behind, replenish by mixing in 600g flour and 300ml water. Leave to ferment for 12 hours until foamy and yeasty before use.
If you’re not planning to use the starter dough within the next 24 hours, refrigerate it. It will keep for up to 2 months.
To use, remove from refrigerator a day ahead. Leave at room temperature from morning until mid afternoon. Replenish with 600g flour and 300ml water for every 50g starter dough. Allow to ferment until needed.