Make the Dough: In a large bowl, whisk the starter and water together with a fork.

Add the flours and salt. Combine to form a stiff dough, then finish mixing by hand to fully incorporate the flour.

Cover with a damp towel and let rest (autolyse) for 30 minutes. This rest period allows the flour to hydrate without interference.

After the dough has rested, add the olives, thyme, lemon zest, and parmesan cheese (if using) to the bowl.

Gently knead the fillings into the dough, using the stretch and fold technique. To do this: stretch the dough upward and fold it over toward the center of the bowl.

Give the dough a turn and repeat (stretching, folding and turning) until the fillings are tucked into the dough. This preserves the gluten structure.

Cover the bowl with lightly coated plastic wrap and let rise at room temperature until double in size. This will take about 8 to 10 hours at 70 F (21 C).

Optional Step: If you’d like, for added structure, perform 1-2 sets of stretch and folds during the bulk rise, spaced 30 minutes apart.

Remove the dough onto a lightly floured surface. Shape it into a round or oval and let rest for 5 to 10 minutes.

Line a proofing basket with a towel and dust generously with flour. With floured hands, gently cup the dough and pull it toward you to tighten its shape.

Place the dough into your basket, seam side up.

Second Rise: Cover the dough and let rest until noticeably puffy but not fully risen, about 30 minutes to 1 hour, depending on temperature. Alternatively, chill the dough overnight, up to 8 hours. Let rest at room temperature while the oven heats up before baking.

Preheat your oven to 450 F (230 C). Cut a sheet of parchment paper to fit the size of your baking pot.

Score: Place the parchment over the dough and invert the basket to release. Sprinkle the dough very lightly with flour and rub the surface to coat. Make one long, off-center cut down the length of the loaf using a small knife or razor blade (hold your blade at a 45-degree angle for an ear).

Use the parchment to transfer the dough into the preheated, covered baking pot.

Bake the dough on the center rack for 20 minutes, covered (Stage 1: Steam for oven spring).

Remove the lid, and continue to bake for 30 minutes at 400°F (Stage 2: Develop color and character).

Lift the loaf out of the pot and finish baking directly on the oven rack for the last 10 minutes (Stage 3: Crisp the bottom crust).

Cool for 1 hour before cutting into slices. Listen for crackling sounds, indicating a perfect bake.