Preheat oven to 180ºC . Grease a 12-cup Bundt pan and dust with unsweetened cocoa powder. Over a large bowl, sift both flours, cocoa powder, baking soda, and salt. Mix in both sugars until there are no lumps. Set aside. Put the peeled potato into a large food processor. Using the steel blade, process the potato until finely minced. Drain the yogurt of all excess liquid. Discard excess liquid. Add the drained yogurt, honey, vanilla, chocolate flavor, and vegetable oil to the minced potato in the food processor and mix on high for 60 seconds. Be sure to scrape the sides of the bowl while processing. Pour this mixture into the bowl of dry ingredients and beat with an electric beater on high for 60 seconds. Be sure to scrape the sides of the bowl while beating. Clean and dry the beaters well. In another bowl, beat the egg whites until soft peaks form. Fold the egg whites into the batter until everything is mixed well. Pour the batter into the prepared Bundt pan. Bake in a preheated oven for 55 to 65 minutes or until a cake tester comes out clean. Remove the cake from the oven and let cool for 25 minutes. Do not be concerned if the cake falls slightly. Using a knife, go around inside and out side edges of cake. Invert the Bundt pan over a plate and carefully shake the cake loose. Let the cake cool completely and frost with a chocolate glaze.