Rehydrate starter with 75 grams water, set aside. (Or 125 grams 100% hydration starter)

Mix both flours, then add remaining water until it forms a cohesive ball. Cover with plastic wrap and set aside for 30 minutes.

Combine starter and yeast (and rosemary if desired), then add to flour ball (mixing with bare hands at first worked best for me). Once moisture is absorbed, mix with dough hook for 9 minutes.

Mid-way through the kneeding process add salt.

Once dough ball passes the window pane test, set aside and cover in a bowl with plastic wrap until doubled in volume. For my starter, this takes several (4-6) hours.

Gently deflate then form into a ball and let it rest for 15 minutes covered.

Shape into a boule or batard, place on sheet of parchment paper, then cover until doubled in size (this should take about half as long as the first rise).

Preheat oven with baking stone to 525°, placing a broiling pan on bottom shelf.

When done rising, slash, lightly spritz loaf with water, then sprinkle with coarse salt to taste.

Using peel, slide loaf (still on parchment) onto stone, pour 3/4 cups of boiling water into broiling pan and immediately reduce temp to 475°. Be careful not to drop water on oven window, or it will shatter. The immediate steam generated can be dangerous, so i use a long necked flower watering pot for this.

Cook until internal thermometer reads 200° (I don't insert thermometer until crust has formed (about 15 minutes)).

Let cool completely on wire rack. Dont be tempted to cut into it while it's still warm, because the internal heat is still cooking and releasing moisture in a controlled manner.

Dinner Roll Option: Roll 80 gram balls and proof. Turn oven down to 450°, spritz rolls with water then crack salt over them. Bake for 15 minutes. Let cool on rack 15 minutes before serving.