Mix together the flours, salt and yeast in a round-bottomed mixing bowl. Add the water, which should be blood temperature. Use a plastic dough scraper to bring the mix together - it will be quite sticky. Beat the dough vigorously with the scraper for about half a minute, no more. Cover the bowl with a plastic lid, or place the whole bowl inside a large plastic bag (don't let the plastic touch the dough).
After 30 minutes, remove the lid/bag and wet the surface of the dough with a few splashes of water (it should pool a bit around the edges). Use the scraper to release the dough from the sides and bottom of the bowl. Now wet your hand and lift up the dough from underneath, holding it in the middle so it stretches down on either side of your hand. Put it back down the same way up before it tears, then turn the bowl by a sixth and repeat. Do this four more times (six in total). You will notice the dough getting stronger and smoother - each time, hold it as long as you can without it tearing.
Repeat this in thirty minutes intervals, two more times, decreasing the amount of added water each time. Leave for another thirty minutes.
Flour the top of the dough, and generously flour a work surface. Release the dough from the sides of the bowl with the dough scraper and turn out upside down onto the floured worktop. Working towards you, start to roll the dough up, folding the top edge in and pressing firmly with your fingers to hold it there. Be really careful not to tear the dough. Repeat two or three more times until you reach the near edge, then make a really good tight seam by pressing along it with your fingers. Turn the dough seam down and use your hands to even out the shape. When you are happy, flour the dough heavily all over and under - pile it quite generously on the top.
Line a baking tray with baking parchment and place it alongside your dough. Carefully lift the dough onto the tray, giving a very gentle stretch as you do so - this will crack the flour on top and give a brilliant finished look to your bread. Carefully place the tray inside a large plastic bag (a recycling bag is ideal), with the opening to the side, being careful not to brush it against the bread. Lightly puff up the bag with a flick of your hands, then twist the opening to trap the air and keep the bag domed over the tray. Tuck the opening under the tray to hold the twist in place.
Heat the oven to maximum (250c is ideal). Place a shelf in the middle, and place and a heavy based tray or ovenproof frying pan on the oven floor.
Leave you bread to rise until more than doubled in size - be patient! When you are ready to bake, boil half a kettle of water and VERY carefully remove the tray from the bag. Spray the bread very generously all over with water from a spray bottle. Place in the oven, pour boiling water into the tray/pan and shut the door as quick as possible. Don't open the door for the first seven or eight minutes.
Bake at as hot a temperature as you dare for up to 50 minutes - I like a really dark, burnished crust. Leave to cool on a wire rack.
«This dough is quite sticky. Don't be tempted to add more flour - it is the stickiness that makes the dough really light and crusty. »