To make Poolish mix: Combine bread flour, water and yeast. Cover with plastic wrap and let sit 14 to 16 hours.

To make bread: Mix semolina flour, durum flour, water and Poolish mix and let sit for 10 to 15 minutes. Add salt and yeast and mix until well blended. Turn dough onto floured surface and knead for 5 to 6 minutes. Dough should feel elastic when pulled. Add toasted sesame seeds and knead gently until evenly distributed.

Turn dough into a well-oiled bowl (with enough room for dough to double in size) and cover with plastic wrap. Let sit for 1 hour, punch down, cover and let it rise again for 1 hour or until doubled in size. Turn dough onto a well-floured surface, divide in half and let sit for 10 minutes. Shape each half into a baguette shape, then form into an “S.” The dough can also be divided into 50-gram pieces and shaped into rounds for rolls. Top with raw sesame seeds, if desired.

Line a tray or board with parchment paper. Let the shaped dough rise on parchment paper (oil tops with olive oil and cover with plastic wrap) for 1 hour or until doubled in size. Set pizza stone or inverted baking sheet on middle rack of the oven. Place lava rocks in cast-iron skillet and set at bottom of the oven. Pre-heat oven to 500°.

When ready to bake, slide dough on parchment onto the heated pizza stone or inverted baking sheet in the oven. Quickly throw about 2 cups of ice into cast-iron skillet containing lava rocks and shut the oven door. (This will create steam in the oven.) Drop temperature to 450°. Bake for 30 minutes. To check for doneness, the bread should have a rich dark brown color and should sound hollow when the bottoms are tapped or knocked. Let loaves sit and cool on wire racks before slicing.