To make the sponge, mix the yeast with the warm water until the yeast is dissolved. Add the light corn syrup to the yeast and water. Mix in the bread flour until there are no lumps in the mixture. Let the mixture rest until a thick surface forms and it is light and spongy.
Boil the potatoes as you would to make mashed potatoes, drain, mash them, and place them in a mixing bowl.
In a separate bowl, combine the milk and yeast, and mix until the yeast is dissolved.
Place the wheat and bread flour in the mixing bowl, add the salt, honey, and milk mixture, and using a dough hook, mix for 2 minutes on low speed until ingredients have combined. Add the sponge to the mixture and mix on medium speed for 8 minutes.
Once the dough is mixed, let it rest for 15 minutes. On a lightly floured surface, cut the dough into 2 equal parts, roll into balls, and let the dough rest for 15 minutes.
Preheat oven to 375 degrees F.
Take the dough balls, and shape them into 16-inch long bread loaves. Brush on a light coating of egg wash on top of each loaf, place the loaves on a baking sheet, and bake them for 35 to 45 minutes.