Add the sugar gradually.
Beat in the eggs in a slow stream. With a fork, beat in 1/3 of the flour mixture, 1/2 the bananas another 1/3 of the flour mixture, the rest of the bananas then the last of the flour mixture. Fold in the walnuts.
Turn into a greased and floured baking unit or a 2 1/2 quart mold and cover. Place on a rack in the slow cooker.
Cover the cooker, but prop the lid open with a toothpick or a twist of foil to let the excess steam escape.
Cook on high for 4 to 6 hours.
Cool on a rack for 10 minutes. Serve warm.
Serves 4 to 6.