Sift together the flour, baking powder, baking soda and salt.

With the electric beater on low, fluff the shortening in a small bowl, until soft and creamy.

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 excape.

Cook on high for 4 to 6 hours.

Cool on a rack for 10 minutes.

Serve Warm.