In a large bowl, add the water and sourdough starter. Whisk them both until they are fully combined. Add the flour and salt. Mix them all until a shaggy dough forms and all the flour is fully incorporated. No dry spots should remain. Cover the bowl and let your dough rest for 20-30 minutes.
Perform your first set of stretch and folds:Stretch one side up and fold it over the center. Rotate the bowl 90 degrees and repeat this for a total of 4 times. Cover the bowl and let the dough rest for 20-30 minutes.Perform a second set of stretch and folds using the same method. Cover and let it rest for 20-30 minutes. Your dough should feel smoother and slightly elastic at this stage. This step is important before adding butter. Sprinkle half of the grated butter over the dough then perform a gentle stretch and fold set to incorporate it. Don't worry if it looks messy at first. It will come together. Cover and rest for 20-30 minutes.
Add the remaining butter and perform another set of stretch and folds. If the dough becomes too soft or the butter starts melting, place the dough in the fridge for 5-10 minutes, then continue. The dough should become smoother but still be soft and slightly sticky.
Cover and let the dough rest at room temperature for about 3-5 hours, depending on your room temperature.Watch for these visual signs the dough is ready:Dough has risen by about 50-75%Surface looks smooth and slightly domedSmall bubbles are visible under the surfaceDough jiggles when you gently shake the bowlIt feels airy and lighterPlease do not rely on time alone. Watch the dough. That's what I do. Lightly flour your surface and gently turn out the dough. Gently flatten the dough into a rectangle. Fold the top down to the centerFold the bottom up to the center (like a letter)Roll it up tightly like a burrito and place it seam-side up into a lightly floured banneton. Place the shaped dough into the freezer for 15-20 minutes. This helps firm up the butter, make scoring easier, and hold the shape better during baking.
You have two options:Option A: Room Temperature ProofProof it for 1-2 hoursOption B: Cold Proof (Recommended)Place it in the fridge for 8-12 hoursThe dough is ready to bake when:It has puffed up noticeablyIt springs back slowly when gently pressed (not instantly, and not too slowly either) Place your Dutch oven inside and preheat it to 475°F (245°C).
Remove the dough from the fridge and turn the dough onto parchment paper. Score the top with a sharp blade in your favorite pattern.
Carefully place the dough into the hot Dutch oven and add 4-5 ice cubes between the parchment paper and the Dutch oven wall. The ice creates steam, which helps the bread expand, delays crust formation, and gives you a crisp, golden crust.
Bake the bread covered for 30 minutes. Remove the lid and bake it until it turns golden brown. If the top browns too quickly, loosely cover it with foil. This usually takes 20-25 minutes.
Remove the Dutch oven from the oven and let the bread sit for a few minutes.Then lift the bread out using the parchment paper. Let it cool for at least 1-2 hours before slicing.