Butter or spray with non-stick cooking spray a 9x5x3-inch loaf pan; set aside. Preheat oven to 325 degrees.
2.
Sift flour, baking soda, baking powder and salt onto a sheet of wax paper. Place the grated chocolate in a bowl and stir 1 ts of the sifted mixture; set aside. Mash bananas in a bowl and stir in half-and-half and vanilla; set aside.
3.
In the bowl of an electric mixer, cream butter and shortening on moderate speed for 3 to 4 minutes. Raise speed to moderately high, add half of sugar and beat for 1 minute; add remaining sugar and beat 1 minute longer, scraping down sides and bottom of the bowl. Add the eggs one at a time, beating well after each addition. Blend in banana mixture on low speed. On low speed, blend in flour mixture in 2 additions, beating just until particles of flour have been absorbed. Stir in chocolate by hand.
4.
Pour and scrape the batter into the prepared pan. Bake for 1 hour or slightly longer - until risen, golden brown on top, and a wooden pick inserted in center comes out clean and dry.
5.
Cool on a rack for 3 to 4 minutes. Carefully invert onto a second rack, remove pan and invert the cake again to cool right side up. Sift confectioner's sugar on the top.
