For the sponge:
100g starter - I use a 100% rye starter because it keeps for long periods without refreshing and for the nutty taste
250g strong white flour
For the final dough:
200g strong white flour
100g strong stoneground wholemeal flour
Oil for the work surface and the proving bowl
1. Mix together the sponge ingredients in a large mixing bowl, ensuring that the flour "clears" completely, ie there are no lumps left. There's no need to knead it at this stage. Cover the bowl with a plate and leave the sponge to ferment until there's plenty of evidence of frothy, yeasty activity on the surface. The length of time this takes will depend on how warm it is in the room and how active the starter is. Try to leave it for at least 12 hours so that plenty of flavour develops.
2. Add the ingredients for the final dough and mix to a loose dough in the bowl before turning it out on to your work surface, pouring a little oil on the surface first so that the dough doesn't stick. Knead vigorously for about 10 minutes until the dough passes the window pane test: can you pull it out into a pizza shape without it tearing and so that light passes through little 'panes'? Then the dough is ready to go back into the (clean) bowl to prove. Put a little oil into the bottom of the bowl first and turn the dough over in it so that it is covered. Cover the bowl with a plate again.
3. Leave it to prove until it has at least tripled in size and springs back readily into shape when you push your thumb gently into it. Again, the time this takes will depend on room temperature, but it's best not to leave it in an overly warm room so that the dough can develop lots of flavour as it rises slowly.
4. Turn the dough out onto a work surface and "dimple" it out gently with your fingertips into a large rectangle before folding it in half and turning it 90 degrees and repeating the process. This helps to add structure, but don't press too firmly with your fingers as you want to retain some of the air bubbles. Continue until the dough is in a fairly tight square and round it off with your cupped hands into a ball before placing it in a flour dusted proving basket.
5. Put the basket inside a plastic bag so that the dough doesn't dry out, and put it in a fairly warm place to prove again. It should now rise more quickly than before. Wait for it to double in size.
6. Turn the dough out onto a baking sheet, slash it a couple of times with a sharp knife and spray it with water (this helps to delay the formation of a crust so that it will rise more. Some people use a metal mixing bowl as a cloche to create an extra humid atmosphere around the bread). Bake at 230 C for 15 minutes and then 190 C for a further 15 minutes until the base of the bread sounds hollow when you tap it. Leave it to cool on a wire rack, and then enjoy!