1
Activate the Starter. Mix 150g of sourdough starter, 75g of flour, and 75g of water in a bowl. Stir until smooth, cover, and leave it somewhere warm for 5 hours to activate. It should roughly double and dome on top. If it has not risen, do not bake with it - feed it again and use it when it doubles reliably within six to eight hours.Note: If you already have an active starter, skip this step and proceed directly to mixing the dough.
2
Mix the Dough. Combine 300g of activated starter, 500g of very strong flour, 300ml of water, and 13g of salt in a mixing bowl. Use a tabletop mixer with a dough hook and mix for about 5 minutes until combined.The dough will be sticky; cover the bowl and let it rest for 30 minutes.
3
Stretch and Fold. Perform the Stretch and Fold technique 3 to 4 times at 30-minute intervals.After each round the dough gains strength and goes from slack and tearing to smooth and springy. It is ready to shape when it has risen noticeably, looks domed rather than flat, and wobbles as one mass when you nudge the bowl, which in a cold kitchen can take longer than two hours. There is a video in the post if you would rather see it done.
4
Shape the Dough. Lightly flour your worktop and stretch the dough into a rectangle. Roll it tightly into a loaf shape and place it seam-side up in a floured proofing basket. If you don’t have a basket, use a bowl lined with cling film.
5
Cold Proofing. Cover the dough and refrigerate overnight. The cold slows the yeast right down while the bacteria keep working, which is where the deeper flavour comes from, and a cold firm dough is far easier to turn out and score.
6
Preheat the Oven. Heat your oven as hot as it will go - mine reaches 275°C - with a Dutch oven inside for at least 25 minutes. What matters here is the heat stored in the cast iron rather than the number on the dial, so if your oven tops out at 240 or 250°C, give it a longer preheat and a couple of extra minutes on the bake.If you don’t have a Dutch oven, use two stainless tins as an alternative (these preheat in 15 minutes).
7
Prepare the Dough. Transfer the dough from the fridge onto baking parchment, seam-side down. Dust with flour and score the surface with a sharp knife or baker’s lame to allow controlled expansion.
8
Bake the Bread. Carefully place the dough into the preheated Dutch oven with the baking parchment, cover, and bake for 20 minutes. After 20 minutes, remove the lid, reduce the oven temperature to 225°C, and bake for another 20 minutes.
9
Cool the Bread. Remove the bread from the oven and transfer it to a cooling rack. The internal temperature should be 96°C or above for fully cooked bread.