Make the Dough:

• Note: you will want to keep your dough temperature between 69 – 73 degrees F so that the butter does not melt and the dough can still rise.  Keep a thermometer handy so you can take the temperature of the dough periodically to ensure it stays between these temperatures.  If the dough gets too warm, place it in the refrigerator until it cools down and retest the temperature.  
• Whisk the starter and water in a large bowl. Add the flour & mix everything together until all of the flour is absorbed. The dough will be dry and shaggy. Cover the bowl with plastic wrap, reusable wrap or a clean, damp kitchen towel. Let the dough rest (called autolyse) for 30 minutes or up to 1 hour, if preferred.
• After the dough has rested, work the salt into the dough and cupping the bottom of the dough, raise it and slap it against the side of the bowl working in circular motion for 2 minutes to help create a stronger elasticity and strength in the dough.  It will look less like a shaggy mess, then lightly cover again and let it rest for 30 minutes. 

Bulk Fermentation:

• During bulk fermentation you will do a series of stretch and folds to the dough.  This process creates a strong crumb structure in your loaf and is the most important part of the sourdough process.  It takes about 4 hours in a warm room.  In colder months it could take an additional 1-2 hours.  

Stretch & Fold the Dough:

• After the dough has rested for 30 minutes, add half of the cold butter to the dough then gather a portion of the dough, stretch it upwards and then fold it over itself. Rotate the bowl ¼ turn and repeat this process until you have come full circle to complete 1 turn. 4 folds = 1 turn.  After each turn, cover the dough and repeat this process every 30 minutes until you have completed 4 turns.  Add half of the butter to the first turn and the rest of the butter to the second turn.  After the 4th turn, cover the dough and leave it untouched for at least an additional 2 hours.  

Pre-Shape the Dough and Bench Rest:

• Remove the dough from the bowl, and place onto a lightly floured work surface so that it does not stick. You do not need to ‘punch down’ the dough; it will gently deflate as you fold and shape it.
• This recipe is for a single loaf but if you would like you can cut the dough in half to make 2 smaller loaves, or leave it whole for a single loaf.
• To shape the dough start at the top, fold the dough over toward the center. Give it a slight turn, and then fold over the next section of dough. Repeat until you have come full circle, basically just another fold. 
• Then flip the dough over and place it seam side down. Using your hands, gently cup the sides of the dough and rotate it, using quarter turns in a circular motion. You can also pull it towards you to even out the shape. Repeat this process until you are happy with its appearance.
• Leave the dough on the work surface and cover it with the bowl you mixed it in, letting it rest for about 30 minutes.  

Final Shaping and Rise:

• Prepare a banneton or other bowl you would like to proof the dough in.  Liberally flour the banneton or bowl.
• Lightly flour the top of your pre shaped dough then using a bench scraper, turn over the dough so the floured side is down.  Gently fold all the corners of the dough into the center being careful not to deflate the dough.  Gently flip the dough over and pull the dough towards you in a circular motion to create tension on top just like you did in pre-shape. 
• Using a bench scraper to support the dough, lift up the dough and set it inside the bannaton or bowl with the seams facing up.  
• You now have 2 options.  You can do a final rise for 2 hours or you can cover and place in the fridge overnight to slow down fermentation.  If you place it in the fridge, take the dough out in the morning and let it sit on the countertop for 1-2 hours before baking.   

Score the Dough:

• With about 45 minutes left during your final rise, preheat the oven to 450 degrees F and place your cast iron pan or whatever pan you are using inside to give them a chance to get nice and hot.  
• Once heated, remove the pan out of the oven and carefully and swiftly turn the dough into the hot pan.  
• Right before your bread goes into the oven, make a shallow slash about 2-3 inches long (or more) in the center of the dough. Use a bread lame, sharp pairing or a small serrated steak knife. The cut should be about 1/4-inch deep.

Bake the Dough:

• Place the bread into the oven on the center rack (lid on) and bake for 20 minutes. Remove the lid, and continue to bake (uncovered) for an additional 15 – 25 minutes or until deep, golden brown. Keep in mind that all ovens are different; you might have to make minimal adjustments to these temperatures.
• You can also take the internal temperature of your bread to double check that it is done. For sourdough, it should read about 205-210º F/ 96-98º C.
• Once the bread is to the desired color remove the pan from the oven and immediately transfer the loaf to a cooling rack.  When you tap the bottom of the loaf it will sound hollow.  Let the loaf rest for 20 minutes before cutting into it.  Serve with butter, jam, or dip in oil.  This bread makes the best grilled cheese sandwiches as well.  
• Note: You will notice that there is butter at the bottom of the pan.  As the dough heats up, butter will melt out of the dough as it bakes giving it the delicious crispy crust.