Sourdough bread baked in a cast iron combo cooker

Put the closed combo cooker into a cold oven and preheat to 500 Fahrenheit until it is smoking hot.

Make the levain: 35 grams of starter, 35 grams of bread flour, 35 grams of whole wheat and 70 grams of room temperature water, mixed with a spatula.

Cover loosely with a lid that is not screwed down and leave five hours, until bubbling and active.

Mix 810 grams of bread flour with 90 grams of whole wheat flour by hand, 900 grams in total.

Add 600 millilitres of warm water and mix by hand only until the flour is hydrated -- no kneading and no gluten development yet.

Cover and rest one hour.

Add all the levain on top, wet your hands, dimple it in, then scoop and slap the dough back down for about two minutes until it smooths out.

Cover and rest 20 minutes to start fermentation.

Dissolve 18 grams of salt in the reserved water, pour it in and dimple it through.

Turn out and slap and fold, turning 90 degrees each time and picking the dough up from underneath, for three to five minutes until smooth.

Return to the bowl, cover and rest 15 minutes.

Do a set of stretch and folds around the perimeter, stretching without tearing, then cover for 15 more minutes.

Turn out, divide in two, pre-shape into rounds and rest three minutes so the gluten relaxes.

Flour the bannetons. Flour the top of each round, flip, fold the sides up and over, roll it down and seal the bottom.

Place seam side up in the floured banneton and stitch the top shut, then cover loosely and retard in the fridge.

Turn the loaf out onto the floured hot base -- rice flour is better than AP here -- flour the top, and score once at about a 45 to 30 degree angle, a quarter to half an inch deep.

Cover and bake 20 minutes, then take the lid off and lower the oven to 450.

Cool on a rack about an hour before cutting, or the loaf loses a lot of goodness.