Sourdough Build:

1. Add the sourdough starter to a medium bowl, pour in the warm water and stir to break up the starter. Mix in the flour and incorporate thoroughly using a wooden spoon or Danish dough whisk. Cover the mixture and let it rest overnight at room temperature for 8 – 12 hours or until ripe.

Final Build:

1. The next day, mix together the levain and all but 50 grams of the water in a large bowl. Add in the flours and stir or whisk the ingredients until thoroughly combined.
2. Add in the chopped rosemary and let the dough autolyse (rest) for 20 – 30 minutes, then add in the salt and the additional 50 grams of water and mix until the salt is completely incorporate into the dough.
3. Cover the bowl and let the dough bulk ferment for 2 hours. Fold the dough 2 times at 30 minute intervals during the first hour. Let the dough rest the final hour.
4. Shape the loaf into an oval shape or the shape of your choice and place it on parchment paper sprinkled with cornmeal. Alternately, place the dough in a brotform proofing basket sprinkled with rice flour. Let the loaf proof for 1-2 hours being careful not to let it overproof.
5. At least 45 minutes before you plan to bake the loaf, preheat the oven to 450 degrees F. with a baking stone on the bottom rack and a steam pan or iron skillet on the top shelf.
6. When the loaf is ready, score it down the middle or in the pattern of your choice and slide it and the parchment paper onto the preheated baking stone. Carefully add 4-5 ice cubes in the steam pan and immediately close the door.
7. Bake the loaf 25-35 minutes. Partway through the bake cycle, remove the parchment paper and rotate the loaf for even browning. When done, the loaf should be browned and sound hollow when thumped on the bottom.
8. Remove the loaf to a wire rack to cool completely before slicing and serving.