This recipe makes a loaf of around 650g (about 1½lb).
400g strong white bread flour
220ml filtered water at room temperature
100ml sourdough starter at room temperature
1 teaspoon sea salt
In the evening, get the sourdough starter out of the fridge and bring it up to room temperature for about 2 hours (it should foam and bubble). Make the sponge by mixing the sourdough starter, water and half the flour but not the salt and leave in a bowl covered with cling-film overnight.
In the morning the sponge should be fermenting (thick and bubbly). Add the other half of the flour and salt and mix well. Add more flour or water if necessary but keep the dough as sticky as possible.
Turn the dough out onto a lightly floured surface and knead until the dough is smooth and satiny (around 10 minutes).
Shape the dough and place it in the floured banneton, sprinkle flour on top, cover with a tea towel and prove in a warm place for two to three hours until nearly doubled in size.
Invert the dough onto a baking dish, slash the top, cover with the cloche, put into a cold oven and bake at 230°C (190°C fan), 450°F or gas mark 8 for 25 minutes once the oven has come up to temperature.
Remove the cloche and bake for another 25 minutes until golden.
Turn the oven off and leave the bread in the cooling oven, with the oven door slightly open, for another 5 minutes, then turn the loaf out onto a rack to cool for at least an hour.