2 1/2 cups tepid water (80 degrees F to 90 degrees F)
2 1/2 cups whole wheat flour
1 tablespoon salt
1 tablespoon olive oil
2 1/2 to 3 1/2 cups unbleached all-purpose flour
For the sponge, in a large bowl, combine the yeast and water, mix well. Using a wooden spoon, stir in 1 cup of the wheat flour at a time. Stir until the mixture is smooth and silky. Cover the bowl with plastic wrap and let rest for 1 hour. Sprinkle the sponge with the salt. Stir in the olive oil. Stir in 1 cup of the flour at a time and mix until the dough is too stiff to stir with the spoon. Turn the dough onto a lightly floured surface and knead until it is smooth and elastic, 8 to 10 minutes. Transfer the dough to a lightly oiled bowl and cover with plastic wrap. Set the dough in a draft-free area and allow to rise until double in size, about 2 to 3 hours.
Line the bottom rack of the oven with baking stones. Leaving a 1-inch border free around the tiles so that the heat can circulate properly. Preheat the oven to 450 degrees F. Turn the dough out onto a lightly floured surface. Knead the dough a couple of times and divide in half. Cover one half of the dough with plastic wrap while working with the other dough. Divide the dough into 8 equal pieces and roll into 8 balls. Using a rolling pin, roll each ball of dough into a circle 8 to 9 inches in diameter and less than 1/4-inch thick. Place each circle of dough next to each other on a parchment lined baking sheet and cover with plastic wrap. Repeat the above process with the remaining dough. Bake the circles of dough in batches, about 4 to 6 rounds at a time. Bake for 3 to 4 minutes, or until the breads look like blown-up balloons. Remove from the oven and cover with a kitchen towel until the remaining rounds are baked. To Store: pita bread is best is used the day it is made, but it can be wrapped airtight and frozen for 1 month. Thaw and reheat on a baking sheet in a 350 degrees F over before serving