Step 1Drain the spinach well, squeezing out any excess liquid. If using leaf spinach, coarsely chop it. You should have 2 cups of drained spinach, packed.
Step 2In a medium bowl, combine the spinach with the oregano, thyme, basil, garlic, pine nuts, ricotta and cornmeal. Season with a scant half teaspoon of salt and one-fourth teaspoon of pepper. Taste, and adjust the seasoning as desired. Cover and refrigerate the filling until needed.
Step 1In a small bowl, whisk together the 2 eggs, sugar, oil, salt and water.
Step 2In a large bowl, whisk together the all-purpose and wheat flours along with the yeast. Make a well in the center of the dry ingredients, and pour in the wet ingredients. Mix together with a wooden spoon until the dough is uniform but still somewhat sticky.
Step 3Transfer the dough to a lightly floured board and knead until it is smooth and soft, and when you poke the dough with your finger the hole springs back immediately, about 5 minutes.
Step 4Place the dough in an oiled bowl and cover with a kitchen towel or plastic wrap. Set aside until doubled, about 1 hour.
Step 5Heat the oven to 350 degrees. Line 2 baking sheets with parchment paper and remove the filling from the refrigerator.
Step 6Divide the dough in half, and place each half on a baking sheet (if the dough is sticky, flour it lightly). Stretch each half on the diagonal of the baking sheet into an oval measuring roughly 16 1/2 inches long by 8 inches wide. Use your fingers to pat and stretch the dough, or a small rolling pin if desired.
Step 7Place half of the filling in a strip down the center of each oval, packing the filling tightly so the strip is no more than 2 1/2 inches wide, and leaving a little space at the top and bottom of the dough to fold it over the filling.
Step 8Use a sharp knife, scissors or a pizza cutter to cut strips 1 1/2 inches wide down the side of the dough on the diagonal, like a feather. Fold the top of the dough over the top of the filling, tucking the edges under.
Step 9Braid the challah: Overlap 1 strip from each side over the other side and the filling, pinching the tips of the strips down where they land. The filling will show through. When you get to the bottom, fold the bottom of the dough over the bottom of the filling and tuck the edges under.
Step 10Brush the loaves with beaten egg, and sprinkle with sesame seeds. Bake until puffed and nicely brown, about 30 minutes. Serve warm or at room temperature. The bread may be prepared up to 1 day in advance, refrigerated and reheated before serving.