METHOD
1. Prepare your sourdough starter as in Tartine country bread instruction. You can also use old starter that has been sitting in the fridge; it will happily revive.
2. The whole process happens over 3 days: making leaven on the night of day 1; working the dough on day 2; shaping the loaf and baking on day 3.
3. The night of day 1 prepare the leaven: discard all but 1 tbsp. of the starter. Mix it with 200g warm water until dispersed. Add the flour, stir it until combined and leave at room temperature for 12 hours. It should become bubbly and puffed up. To test if it’s ready, scoop a teaspoon of it and see if it floats in a bowl of water. If it sinks, let it mature longer.
4. For the main dough, mix 125g of the leaven (the rest will become your starter for future baking and can live in the fridge) with 350g warm water in a large bowl; stir to disperse. Add the honey, the 400g white flour and the 100g wholemeal and mix to a rough dough with your hands or a dough whisk until there is no more dry flour visible. Cover the bowl with a damp tea towel and leave to rest for 25-40 minutes at room temperature.
5. Add the salt and the remaining 25g of warm water to the dough and mix with your hands, the dough whisk or in a standing mixer with a dough hook attachment until it smooths a little and starts pulling away from the sides of the bowl. Cover with the damp tea towel and leave in a warm place for 30 minutes.
6. For the next 3 hours stretch and fold the dough every 30 minutes, then return it to the warm place. To do that, wet your hands; grab the underside of the dough at one quadrant and stretch it up over the rest of the dough. Repeat this three more times, rotating bowl a quarter turn for each fold. Do this every half an hour, six times in total.
7. At the end of the session the dough should increase in volume 20 to 30 percent.
8. Cover the bowl with cling film and place in the fridge for up to 24 hours.
9. The next day take it out early, so it returns to room temperature; it will take a couple of hours.
10. When it gets warmer, scrape the dough onto a floured surface and divide it in half. One piece at a time, pull the dough to a rough rectangle and tightly roll it from the farthest long end towards you, Swiss roll-style, pinching the end of the dough to seal. Leave the pieces of dough on the work surface seam side up and cover loosely with a cloth or oiled cling film. Let it rest for 20 minutes.
11. In the meantime prepare a 13” Pullman tin or a 13” ordinary loaf tin by buttering it thoroughly, including the lid. If you’re using an ordinary tin, butter a length of double layered aluminium foil to cover the loaf tin.
12. To form the loaf, place both pieces of dough 5mm away from each other on a floured work surface. Grasping one of the short ends with each hand, twist the dough in opposite directions to make an interlocked spiral.
13. Slide both hands, palms upward, under the twisted dough and invert it, seam side down, into the prepared tin. If using the Pullman tin, slide the cover about 2/3 of the way across the top of the tin. If in an ordinary tin, place it in an inflated large plastic bag (just blow into it and tie the ends!). Let the loaf proof until it is about 1cm away from the top of the tin.
14. Set a rack in the lower third of the oven and preheat to 220C/425F/gas mark 7.
15. Once the dough has risen so that it is only 1cm away from the top of the tin, slide the Pullman cover closed or cover the ordinary tin tightly with the foil, buttered side inside. Place the tin in the oven. Bake for 30 minutes, then slide the lid off the Pullman or take off the foil; and continue for another 15 minutes.
16. Remove the loaf from the oven and turn it onto a rack to cool.