1 tbsp yeast
1 cup sourdough starter
1 ½ cups bread flour & 1 ½ cup Italian flour
2 tsp sugar
2 tsp salt
1 tsp baking soda
½ cup bread flour & ½ cup Italian flour
Flour for kneading
Place water in a large bowl and add yeast and stir till dissolved. Add starter and stir till combined. Add first 3 cups flour, sugar and salt and stir hard for 2 or 3 minutes. Notate where the level of the dough is. Cover with a cloth and place in warm place and let rise 1-1/2 to 2 hours or until doubled in size.
Combine baking soda with remaining cup of both flours and stir into the dough. When combined, turn out onto a floured surface and begin kneading. If needed, you can add additional bread flour to get smooth, non sticky dough. Knead until the dough feels, between 5 and 10 minutes. When you think you have kneaded long enough give that ball of dough a firm poke in the middle with your finger. If the indentation fills back quickly, the dough is ready to rest. If it stays looking like a deep dimple, continue kneading until the hole fills back quickly. It should be smooth and how I describe as "feel like a baby's bottom" - silky smooth and soft.
Divide ball into 3 equal parts. Shape into 3 oblong loaves, If desired you can shape into 1large round loaf, I placed them on a perforated baguette pan.( If you don’t have one place them on a baking stone or heavy cookie sheet that has either semolina flour or cornmeal sprinkled on it. Cover with a cloth, set in warm place, free from drafts and let rise 1 to 2 hours or until nearly doubled in size.
When dough has risen, brush outside with water and make diagonal slashes across the top with a very sharp knife or single-edge razor blade.
In the bottom of the oven place a shallow pan. Fill pan with hot water. It may be necessary to refill pan with hot water during baking process.
Bake at 400° F for 35-45 minutes or until the crust is golden brown or has a hollow sound when thumped.