This is the bestest one for noooooobs
100 grams prepared starter (such as King Arthur Classic Fresh Sourdough Starter, $8.95)
200 grams (about 1 1/4 cups, plus 2 tablespoons) unbleached all-purpose flour
100 grams (about 2/3 cup) whole wheat flour
6 grams (about 1 teaspoon) fine sea salt
230 grams (about 1 cup, plus 1 tablespoon) 65F-70F water
Wheat bran, for dusting
1. In a large bowl, combine the white flour, wheat flour, and salt and whisk to combine. In a small bowl, whisk the starter and water until the starter is fully dissolved. Pour the starter mixture into the flour, and use a flexible spatula to quickly mix. Cover the bowl loosely with a clean kitchen towel, and let the dough sit at room temperature for 30 minutes.
2. Turn the dough, pulling it off the sides of the bowl and folding into the center as you turn; work it as little as possible. Cover loosely and let rest for 30 minutes before turning the dough again. After approximately 5 turns, or 2 ½ to 3 hours, the dough should be ready. (Don’t expect to see a big increase in size in this dough—by turning the dough every half-hour, you are doing what I call the lazy man’s version of kneading the dough—improving the texture without much effort.)
Note: How do you tell when it’s ready? You want it to get to the point where it is capable of holding a shape, and not ooze into a pancake when you shape it into a ball. It should be so interested in sticking to itself that it easily peels off the bowl when ready to shape.
3. Place a large piece of parchment paper on a sheet pan and cover with wheat bran, so that you can no longer see the paper. Transfer the dough to a lightly floured surface and form it loosely into a ball: hold it with both hands and gently tug the sides down and under, into the middle of the dough, to make a taut ball; don’t let the dough tear. Set the dough seam side down on the bran-coated paper. Dust the top of the dough lightly with more bran. Cover loosely with the towel and let it sit at room temperature until doubled in size, about 2 hours.
4. Preheat the oven to 500F (450F if your oven runs hot). Preheat a cast-iron ovenproof pot with tight-fitting lid, such as Le Creuset, in the oven. Carefully remove the lid and transfer the dough on the parchment into the pot. Use a serrated knife to score the loaf with a long slash, to allow the dough to expand. Cover the pot immediately and place the pot in the oven.
5. Bake the bread for 35 to 40 minutes with the lid on. Carefully remove the lid and tear off any excess parchment. Bake for another 10 to 15 minutes with the lid off, until the crust is a very, very dark brown. (I urge you to let the bread cook, uncovered, until the top of the bread nearly blackens and the sides reach a very, very, very dark brown.) Remove the loaf from the pot. Cool the loaf on a wire rack. The loaf will continue to cook as it cools, so try to wait an hour or so before cutting into it.