Start the evening before you plan to bake, by refreshing your starter from the fridge: mix 10g of starter and 100 ml water; then stir in 10g of Shipton Mill's Strongest Whole Wheat flour and 90 g White No. 4 flour. Cover and leave in a warm place 8-12 hours, till it has doubled in size and is fairly bubbly. A teaspoonful dropped into a bowl of water should float.
In the morning, mix 105g of refreshed starter with 315 ml of water (warm, 35degrees), then mix in 115 g Swiss dark flour, 115 g strongest whole wheat flour, and 285g white no 4 flour for a total of 515g flour. You can vary the ratio of Swiss dark to whole wheat somewhat, to taste. Leave for ½ hour, covered. Then add 20 ml of water and 10g fine sea salt. Knead by hand – pick the dough up and squish it to distribute the salt, then start pulling, twisting, and squishing it till its texture changes. It should become stickier, and strands should form, for instance when you splay your fingers. The dough will look shaggier as you pull it between your hands.
Return the dough to the bowl and cover. Then, with moistened hands, lift and fold the dough gently four times, through quarter turns, every half hour for around three hours. Once the dough feels puffy and has nearly doubled in size, turn it out onto a lightly floured surface and shape it gently into a ball. Cover it with the upside-down bowl, leave it for twenty minutes and shape again. Dust it with brown rice flour and place the dough into a large proving basket that has been liberally sprinkled with rice flour. Put it into a clean plastic carrier bag, and leave it somewhere warm to prove, 4-5 hours. An airing cupboard works well. If it’s likely to be too late to bake it, you can put it in the fridge for an overnight rise; take it out an hour before you plan to bake it to let it come back to room temperature.
When the loaf has nearly doubled in size and it springs back but not completely or quickly when prodded, it’s ready to bake. Preheat the oven to 230C, gas mark 8, and put a baking tin with water in it on the lower shelf. When the oven is ready, gently turn the loaf onto a baking sheet, slash the top two or three times, and put it on the upper shelf. Bake 10 minutes, till it’s starting to brown, then turn the oven down to 180C, gas mark 5 and bake a further 25 minutes. Cool on a rack covered with a clean tea towel.
Please note that I don’t know how to calculate for a fan-assisted oven. My thanks to Wild Bread Kitchen in Faversham for the basis of this recipe.