To make the sourdough starter
Mix 50g flour with 50g water and leave semi covered for 24 hours.
Repeat this twice more until you have a bubbly mixture known as the starter.
For the levain
Mix the starter, flour and water and mix well.
Cover and leave overnight.
To make the bread
Put the levain into a large bowl.
Add 500g strong white bread flour (or a mix of rye, brown and spelt if you want a wholemeal loaf).
Then add 300ml of warm water.
Mix together to form a rough ball of dough.
Cover and set aside for an hour.
After an hour add 12g table salt.
Mix thoroughly, cover and leave for one hour.
Roughly ever hour, stretch and fold each side in to help develop the gluten. Wet your hands before this to stop sticking.
After the dough has risen, stretch it out on a floured surface and fold and shape your loaf.
Dust a proving bowl or a bowl lined with a tea towel with flour.
Cover and leave to prove in the fridge overnight.
Take the dough out of the fridge and turn on to a piece of grease-proof paper.
Score the bread across the top.
Place the bread in a pre-heated casserole, which has a lid.
Bake with the lid on for 20 mins at 230 degrees c.
Remove the lid and bake for a further 20 mins.
Leave to cool for an hour before slicing.