Wash and peel a small sweet potato. Cut into squares and boil on medium heat until potato is soft, but not mushy. (Do Steps 2 and 3 while it cooks.)
Put 4-1/2 cups of flour into large mixing bowl.
Prepare cup of very warm water by microwaving water on HIGH for 1-1/2 minutes or using very warm tap water. Spoon 4 tablespoons of water into a small bowl. Add 1 teaspoon sugar to water and 2 packets of yeast. Gently stir to dissolve yeast. Set aside for 5- 7 minutes to let yeast begin to foam. Yeast should double in bulk.
When potato is ready, drain. Cool slightly, then grate pieces on very fine setting in hand-cranked grater or ricer, into large mixing bowl with flour. (Potato pieces should be about the size of tiny rice grains.) Mix the potato and flour.
Beat 1 whole egg and 2 egg yolks in a small bowl.
Add yeast mixture to large bowl with flour and potato. Add beaten eggs and rest of warm water, 1/2 cup oil, sugar, honey, and salt. Mix ingredients with a wooden spoon until well blended and the dough no longer sticks to sides of bowl. If the dough is sticky, add more flour.
Place dough onto a clean, flat, floured surface. Sprinkle flour on your hands. Knead the dough, in a strong rhythm of push-fold-push-turn, adding flour to the board and/or your hands until dough is smooth, elastic, and no longer sticky, about 5Ã¢â‚¬â€œ10 minutes. Test the dough by poking your finger into the middle. If it bounces back, it's ready!
Add chocolate chips to the kneaded dough, pressing them into the dough with your fingers and distributing them evenly. Put more than you think you'll need - when the dough rises it will expand and need more goodies.
Wash and dry the large flour bowl and spread 1 teaspoon of oil evenly onto the inside surface to keep the dough from sticking to the sides when it rises.
Transfer dough to bowl. Turn dough so all sides are rubbed with oil. Cover bowl with a clean dish towel and let the dough rise in a warm place until doubled in bulk (about 1 - 2 hours).
Braiding The Challah
To braid the challah, divide remaining dough in half. Divide each half into 3 equal parts. Roll each part into a long cord. (See 1 above.) Pinch three cords together at the top. (See 2 above.) Braid them together. (See 3-7 above.) Pinch the ends together. Repeat with remaining 3 cords.
Grease baking sheets with margarine and sprinkle with cornmeal. Place challot on baking sheets. Cover and let rise in a warm place until doubled in bulk, approximately 1/2 - 1 hour.
When challot are ready, take out a small bowl and mix 1 egg yolk and 1 teaspoon water. With a pastry brush, brush challot with egg mixture.
Bake at 325 - 350 degrees for 30 - 45 minutes, or until golden brown. Test the challot by lightly tapping the sides—if they make a hollow sound, they are probably done. Remove challot from baking sheets and cool.