The day before mixing (2 days before baking), remove your starter from the fridge and begin reviving it.

Move 15g of the cold starter to a clean small (about 8oz) jar and discard the rest.

Add 15g of warm water (about 78 °F) and stir together with the starter until completely integrated.

Add 15g of white flour (all purpose or bread) and stir together until no dried bits remain.

Loosely cover the jar and store at room temperature.

Using the same jar, discard all but 10g of the starter.

Add 30g of water (this time a little cooler, about 73 °F) and thoroughly mix with the starter.

Add 30g of flour and mix thoroughly.

Loosely cover the jar and store at room temperature to rise overnight.

This is the final feed of your starter before baking.

Move 30g of the starter to a clean, larger (about 16oz) jar and discard the rest.

Add 60g of warm water (about 80 °F) and mix thoroughly.

Add 60g of flour and mix thoroughly.

With a rubber band or marker, mark the jar where the top of the starter is so you can track its progress.

Loosely cover the jar and let rise in a warm place.

In a large bowl, add 400g Bread Flour, 40g Rye Flour, and 270g Water (about 80 °F).

Start to squeeze together the ingredients with one hand, keeping a plastic scraper in the other to remove dried bits from the bottom of the bowl as you go.

After a few minutes, the dough should be somewhat integrated and easier to handle.

Using both hands, continue squeezing the dough together, occasionally rolling the dough ball around the bowl to pick up any stray dried bits, until thoroughly combined.

Cover with a damp kitchen towel and let rest until the starter is ready.

In the same bowl, add the 90g Starter on top of the dough.

Store the remainder of the starter in the refrigerator for your next bake.

Begin to fold the dough over onto the starter, repeatedly rotating and folding so the starter begins to integrate, for about 2 minutes.

Using both hands, start squeezing the dough through your fingers to mix in the starter. Be careful not to tear the dough at this stage.

Once the starter is mostly integrated, evenly spread the 9g Salt on top of the dough.

With wet hands, squeeze in the salt, again being careful not to tear the dough, until thoroughly combined, about 3 or 4 minutes. If making more than 1 loaf, it may be easier to knead the dough on a lightly wetted counter. Either method is fine.

Cover with a damp kitchen towel and let rest until the next step.

Using a probe thermometer, take a temperature reading from the center of the dough. Enter this value into the rise widget above.

In the same bowl, perform a “stretch & fold” by gently pulling each corner of the dough out from the middle and returning it to the center.

Cover and let rest until the next fold in 30 minutes.

Again, take the temperature of the dough and enter the average temperature into the rise widget above.

Perform another stretch & fold, again pulling each corner out and returning to the center.

Let the dough rise for another 4 to 6 hours at room temperature, about 70 °F to 74 °F. For warmer temperatures, shorten the bulk rise duration according to the rise time calculator above.

Line a proofing basket with flour.

Lightly flour the counter and gently invert the dough onto it.

If baking more than one loaf, divide the dough into equal pieces using a bench scraper.

Shape the dough by folding each of the four corners of the round into its center.

Move into the proofing basket, seam side up, and cover with a damp kitchen towel.

Proof at room temperature for around 20 minutes.

Move into a cold fridge for up to 16 hours.

Place a Dutch oven or similar pot inside your oven, with the lid on.

Pre-heat the oven to 500 °F for about 30 minutes, with your Dutch oven or similar pot inside.

Remove the basket from the refrigerator.

Carefully invert the dough from its basket onto a sheet of parchment paper so its seam is now facing down.

Dust the top of the dough with flour.

Score the top of the dough using a bread lame or serrated knife, making one or more cuts about ½” deep.

Carefully remove the pot from the oven and remove the lid.

Using the edges of the parchment paper, carefully lift and move the dough into the pot.

With a mitted hand, put the lid back on the pot.

Carefully place the pot in the oven.

Reduce the temperature to 475 °F and bake with the lid on for 20 minutes.

Carefully remove the lid from the pot (briefly remove the pot from the oven if needed).

Bake uncovered at 425 °F for another 25 minutes, or until the crust is a golden brown and the edges of the score marks just start to burn.

Transfer the loaf to a wire rack and let cool for at least 45 minutes before slicing.