Butter or spray a 10x4 or 9x5 inch loaf pan. Line the pan with a strip of parchment paper, covering the bottom and two short sides. The two long sides will remain unlined but greased. This will help you remove the bread from the pan after it’s baked.
In a large bowl beat oil with sugar for 1 minute.
Add eggs, one at a time, beating well after each addition.
Add bananas and vanilla in 2 parts, alternating with sifted dry ingredients (both flours, baking soda, baking powder and salt) in 3 parts. I sift everything directly over the batter, but you can do it separately.
Add chocolate chips or chunks and mix well with a spatula.
Pour into the prepared pan, smooth top and decorate with a whole banana, cut lengthwise in 4 pieces, on top. Sprinkle with the extra tablespoon of sugar.
Bake for 45-50 minutes, until cracked on top, and a cake tester or toothpick comes out clean. Time might vary depending on the oven and the type of pan.
Let cool on a wire rack and remove carefully, inverting the pan and peeling away the paper.
It keeps, well wrapped, at room temperature for a day or two.
Notes
Baking time: consider that all ovens and pans are different, even if they look similar. The baking time in my recipes is as accurate as possible, but it might take you more or less time. You can use a thermometer to check that your oven is at the right temperature. I recommend keeping track of how your oven works and what tiny details you might need to adjust. Bananas:the best ones for this recipe are the overripe, soft, mushy ones that smell barely fermented and have spotted skin.Variations: add some chopped walnuts or pecans to the batter, about ¼ cup, or a few tablespoons cocoa nibs or wheat germ or bran.Freezing: well wrapped it can be frozen for up to a month.