1/3 cup bubbly, active sourdough starter
1 1/3 cups plus 2 tablespoons warm water
2 tablespoons Rosemary Olive Oil
1/2 cup plus 2 tablespoons all purpose flour
3 1/2 cups bread flour
1 tablespoon fresh rosemary, coarsely chopped
1 1/2 teaspoon kosher salt
Step 1: Whisk sourdough starter, warm water, and Rosemary Olive Oil together in a large mixing bowl. Add in the all purpose flour, bread flour, rosemary, and salt. Use a fork to combine, then finish mixing the dough with your hands. The dough will feel very sticky. Cover the dough with a damp towel and let it rest for 30 minutes.
Step 2: Once the dough has rested, use your hands to form the dough into a smooth ball.
Step 3: Place dough back into the bowl and cover it with a damp towel and set it in a warm area of your home. Let the dough rise for 8 to 10 hours.
Step 4: Once the dough has risen, move the dough from the bowl to a flour dusted surface. Shape the dough into a round. The goal is to create a loaf-shaped round. Let the dough rest for 5-10 minutes, uncovered on the work surface.
Step 5: Once the dough has rested, cover the dough with a damp towel and let it proof in a warm area of your home for 45-60 minutes.
Step 6: Cut a sheet of parchment paper to fit the size of your cast iron skillet or dutch oven. Remove the dough from the proofing pan and place it seam-side down on the parchment paper. Dust the loaf with a little more all-purpose flour, then score the dough with your scoring blade, using your desired pattern.
Step 7: Place the parchment paper and dough into your baking vessel and cover with a lid. Bake in your preheated oven (Preheat to 450F) for 20 minutes, covered. Remove the lid using thick pot holders and continue to bake for 30 minutes. Carefully remove the loaf from the baking vessel and place it directly on the oven rack. Bake for a final 10 minutes, to let the crust crisp up.
Step 8: When the bread is done, remove the loaf from the oven and place on a cooling rack. The crust will feel very hard to the touch, but it will soften as it cools. Let the sourdough cool for at least an hour before slicing and serving.