Stir yeast into warm water in a small bowl. Let stand for 5 minutes.
In a large mixing bowl, combine butter, boiling water, cornmeal, molasses, and salt. Mix well. When butter has melted, stir in milk. When the mixture has cooled to lukewarm, stir in dissolved yeast.
Mix in all the whole wheat flour and 2 cups of the unbleached white flour. Beat at medium speed for 2 minutes. Stir in 2 more cups of white flour.
Turn dough onto a well-floured surface. Knead for 10 minutes, adding flour as needed until the dough is smooth and elastic.
Place in a greased bowl. Cover and let rise in a warm place for about 1 hour until doubled in bulk. Punch down. Let rise again until doubled.
Punch down and divide dough in half. Shape into loaves. Place in two buttered 9 x 5-inch loaf pans.
Let dough rise about 30 minutes or until almost doubled in bulk. Place in a cold oven. Set temperature at 375ᵒ F. and bake for 30 minutes. Reduce heat to 350ᵒ F. and bake another 10 minutes or until done. Remove from pans and cool on wire racks.