Dissolve yeast in 1½ cups warm water (about 105°F) in a large bowl and let sit for 10 minutes. Stir in honey, oil, salt and whole wheat flour until flour is moistened. Stir in all-purpose flour, one cup at a time, until a soft dough forms and stir in walnuts.
Turn dough onto a lightly floured counter. Knead, adding flour as needed, for about 5 minutes to form a smooth dough. Place dough into a large oiled bowl, cover with plastic wrap and let rise until it has doubled in bulk, about 1½ hours.
Divide dough in half, form each half into a large ball and place on a cookie sheet that has been sprinkled with cornmeal. Loosely cover with plastic wrap and let rise about 30 minutes or until balls appear puffy.
Preheat oven to 350°F. Sprinkle top of loaves with flour and cut an x into the tops using a serrated knife. Bake 35 to 45 minutes or until a thermometer inserted into the center of the loaves registers 190°F. Cook on a rack, waiting 20 minutes before cutting.
You can freeze half of the dough before the second rising. Defrost overnight in the refrigerator then place on a cookie sheet as indicated in step 3 to let rise and bake.
Kitchen too cold for dough to rise? Place the dough in a cold oven over a pan of boiling water with oven door closed. It will create the moist, warm space you need.