Day 1: In a clean, wide-mouthed jar, mix 50 g strong white bread flour with 50 ml mineral water until smooth. Cover the jar loosely and leave at room temperature (20–24 °C) for 24 hours.
Days 2 and 3: Simply observe the starter without feeding it. Keep the jar in the same spot and watch for bubbles forming and a tangy aroma developing.
Day 4: Discard most of the mixture, leaving about 50 g of starter in the jar. Add 50 g strong white bread flour and 50 ml mineral water, mix well, cover loosely and leave for another 24 hours.
Days 5 to 7 (daily feeding): Every 24 hours, discard most of the starter, leaving 50 g, then feed with 50 g strong white bread flour and 50 ml mineral water. Mix and leave until the starter doubles in volume and is bubbly.
Float test: To check if it’s ready, drop a teaspoon of starter into a glass of water. If it floats, the starter is active and ready to use.
Maintenance: Once active, store the starter in the fridge if you don’t bake daily and feed it once a week. If you bake regularly, keep it at room temperature and feed it every 12–24 hours.