In bowl combine 1-1/2 cups of the flour, the sugar, yeast, and 1 tsp. salt; set aside. In saucepan combine milk and butter. Heat until warm (125 degrees F). Add to flour mixture. Add bananas, eggs, and yolks. With mixer, beat on medium 2 minutes. Stir in 3-1/2 cups flour, adding additional flour 1/4 cup at a time. (Dough will be sticky.) Transfer to a buttered bowl; turn to coat surface. Cover; let rise 1 hour or until doubled.
Fry a few at a time in hot oil (365 degrees F) for 2 minutes or until golden; turning once. Remove with slotted spoon; drain. Dip in glaze. Makes 30 doughnuts plus holes.
In microwave-safe bowl combine semi- sweet chocolate pieces, whipping cream, and butter. Microwave 1 minute; stir. Microwave 30 seconds more. Whisk in powdered sugar until smooth and light-color corn syrup.