adapted from Taste of Home
5 to 5-1/4 cups all-purpose flour
2 cups whole wheat flour
2 packages active dry yeast or 2 TBSP jarred yeast
2-1/2 cups water
1 TBSP sugar
1 TBSP salt
1 TBSP butter
2 TBSP olive oil
1 egg white, beaten
1 tablespoon water
Combine the flours. In a large bowl, combine 3 cups flour mixture and the yeast. Set aside. Heat water, sugar, salt and butter to 115°-120°. Add to flour and yeast. Beat with on low speed for 30 seconds; increase speed to medium and beat 3 additional minutes. Stir in enough remaining flour to make a soft dough. Add olive oil now.I used right at 7 cups total, but you may need more.
Turn onto a lightly floured surface and knead until smooth and elastic, about 6-8 minutes, or use dough hook attachment on mixer to do the kneading for you. Place dough in a greased bowl; cover and allow to rise in a warm place until doubled, about 1 hour.
Punch dough down; divide in half (or fourths if making 4 loaves) and let rest 10 minutes. Roll each piece into a 15-in. x 12-in. rectangle. Roll up jelly-roll style, starting with the long side. Pinch seal and turn ends under to form a smooth loaf. Sprinkle two baking sheets with cornmeal and place each loaf, seam side down, on a greased baking sheet. Make slashes every 2-1/2 in. in the top of each loaf. Cover with greased plastic wrap and let rise until doubled, about 1 hour. You can put them on the same baking sheet, but they will rise and end up sticking to each other.
Beat egg white and water; brush some over loaves. Refrigerate remaining egg mixture. Bake at 375° for 20 minutes. Brush again with egg white mixture and bake 15-20 minutes longer or until golden brown. Remove pans to wire racks to cool. Yield: 2 very large loaves or 4 medium-large loaves .