Preheat oven to 350. Cream together shortening and sugar. Add eggs one at a time, beating well after each addition. Mix in bananas, buttermilk, and vanilla. Mix in flour, baking powder, and soda. Stir in nuts if desired. Pour batter into two greased 9x5 inch pans.
Bake for 50 to 60 minutes in the preheated oven, or until a toothpick inserted into the center of the loaf comes out clean.