In a large bowl, cream shortening and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in bananas and vanilla. Combine, flour baking powder, soda and salt. Add alternately to the creamed mixture with buttermilk. Stir in nuts.
Pour into two greased and floured 9-in. round baking pans. Sprinkle with coconut. Bake at 375° for 25-30 minutes or until a toothpick inserted in the center comes out clean. Cool in pans for 10 minutes before removing to wire racks to cool completely.
For filling, combine the sugar, flour, cream and butter in a saucepan. Bring to a boil over medium heat; cook and stir for 1-2 minutes or until thickened. Remove from the heat. Add nuts, salt and vanilla; cool. Spread filling over one cake layer with coconut side up. Place second layer, coconut side up, on top.
For frosting, in a small bowl, beat the shortening, butter confectioners' sugar, vanilla and enough milk to achieve frosting consistency. Frost sides of cake only. If desired, cake can be made without frosting.