In a small bowl, combine the water, yeast, sugar and olive oil. Let stand until foamy, about 5 minutes. In a large bowl, combine the bread flour, whole wheat flour, salt and 1 tablespoon chopped rosemary. Stir in the wet ingredients until it forms a shaggy dough.

Turn out the dough on a lightly floured work surface and knead until it is smooth and elastic, about 10 minutes.

Shape the dough into a ball. Transfer to a bowl greased with olive oil. Cover and let rise until doubled in volume, about 2 hours.

Divide the dough in half.

On a work surface dusted with flour, roll out the dough into 2 ovals about 12 inches long and 8 inches at the widest point.

Place each oval on a parchment paper-lined sheet pan. Using a pizza wheel, cut two slits down the length of the center of the oval without splitting it in half. Pull them open slightly.

Then make shorter diagonal slashes on either side of the center slits. And again gently pull them open.

Make small cuts around the outside of the oval between the diagonal slashes.

Cover the dough and let it rise and puff up for 30 minutes.

Preheat the oven to 450 degrees F.

Brush the dough with olive oil and sprinkle with flaky sea salt.

Bake for 15-20 minutes until golden brown. In the last few minutes of baking, sprinkle the loaves with the remaining rosemary.