Day 1: 10.00 am

• walnut of leaven from previous baking
• 30 fl oz/1 fl oz cold water
• 60 g/2 oz unbleached white bread flour

Day 1: 5.00 pm

• 100 ml/3½ fl oz tepid water
• the leaven from the previous stage
• 200 g/7 oz unbleached white bread flour

Day 1: 11.00 pm

• 175 ml/6 fl oz cold water
• the leaven from the previous stage
• 350 g/12 oz unbleached white bread flour

Day 2: 8.00 am

• the leaven from the previous stage
• 450 ml/16 fl oz water at 43°C/110°F
• 800 g/1¾ lb unbleached white plain flour
• 30 g/1 oz salt

1. Put the leaven in a bowl and mix with the water, then add the flour and knead to a homogenous dough with your fingertips. Put the dough in a small bowl covered with clingfilm and leave to ripen at about 24°C/75°F. It will at least double in size.
2. Add the water to the leaven to dissolve it, mix in the flour and knead the dough on a floured work surface. Leave it to rise in a bowl covered with clingfilm at about 24°C/75°F. It will at least double in size. It will have a definite smell, vinegary and sharp, but not overly strong.
3. Add the water to the leaven to dissolve it, mix in the flour gradually, then knead it on the work surface for 10 minutes. Leave to rise in a bowl covered with clingfilm at 10°C/50° F overnight. It will at least double in size.
4. Make a soup of the leaven and the water, squeezing it between your fingers to break it up. Mix the flour and salt together, then gradually add them to the liquid, mixing the while. Mix to a dough that leaves the sides of the bowl clean, then knead on a floured work surface for 10 minutes, until smooth and resilient. Leave the dough to rise in a bowl covered with clingfilm in a warm place (24°C/75°F) for between 2 and 3 hours, until doubled in size.
5. Turn out the dough on to the lightly floured work surface, knock back, divide in half and mould each piece into a ball. At this stage, take off a walnut of dough to act as leaven for the next time. Put it in a small bowl, cover with clingfilm and refrigerate. It will keep undamaged for at least a week, and can then be reactivated for another session of baking.
6. This bread can be proved in bannetons (proving baskets), or, with no further moulding, on baking sheets. The shape of the bannetons will determine whether you have to mould it into long loaves or leave them round. Whichever shape, make sure the bannetons are well floured, and prove the loaves bottom upwards as you will be turning them out on to baking sheets, stones or the floor of the oven itself.
7. Leave for a final proof, covered with oiled clingfilm to prevent skinning. If you take a nut of the dough and put it into a storage jar or jug filled with water at room temperature, it will rise to the surface as the yeasts generate gases - just as your loaves are rising in their baskets. When that nut of dough comes to the surface of the water, then your bread is proved and can go into the oven. Proving should take about 1-1½ hours. Meanwhile, heat the oven to 230°C/450°F/gas 8.
8. Turn the loaves on to oiled baking sheets, or a baking stone, slash them with a knife: three slashes close together for round loaves, diagonal cuts down the length of longer breads, and bake them for about 35 minutes, spraying them with water three times in the first 5 minutes. If they do not sound hollow after 35 minutes, bake for another 15 minutes at 200°C/400°F/gas 6. Cool on wire racks.