Combine multi-grain cereal and 1 cup of water in a small pan. Cook over medium-low heat, covered, for 10 minutes, or until soft.
Remove from heat and stir in butter until melted then add the remaining 1 cup of water, honey, and salt. Cool to lukewarm (Use cold water to speed this process).
In a mixer combine the 2 cups of whole wheat flour, yeast, cereal mixture and eggs. Beat at low speed 1 minute, scraping bowl, then beat at high speed 2 minutes.
Using a dough hook (or by hand), stir in 3 cups unbleached flour to make a soft dough.
Knead with hook 3 minutes (or by hand 5-8 minutes), using remaining flour, if needed. (NOTE: don't add too much flour at this point when using the 2 cups whole wheat - the dough will still look sticky on bottom and sides of mixing bowl, but will not be sticky to the touch.*)
Place in a greased bowl, turning to grease all sides. Cover and let rise until double, 1 to 1 ¼ hours.
Punch down and turn out onto a lightly floured surface. Divide in half, cover and let rest 5 minutes.
Shape into 2 loaves and place in 9x4-in pans. Cover and let rise in warm place until doubled, 45 to 60 minutes.
Combine the egg yolk with 1 Tb. water and brush on tops of loaves. Sprinkle with sesame or poppy seeds.
Bake at 375 degrees for 30-35 minutes. Turn out of pans and let cool completely on racks before slicing.
*The original recipe called for all regular flour, I found when I used whole wheat for the first 2 cups that it didn't need a full 3 to 3-1/2 cups flour, only about 3. If using all unbleached flour, use the 3 to 3-1/2 cup recommendation.