A note on pans. My original recipe upon which this Frankensteinian version is based fills a 9-by-5-inch loaf pan. I think this one would squeeze into that size, with an increase in baking time and you'd probably have to tent it with foil towards the end, too. The trouble is, with all the extras added, I'm not absolutely certain that it would emerge with an impressive crown rather than ooze all over the oven. If you give it a go, please report back with your findings.
To that end, and as the last thing I want to do is lead you astray, the directions below reflect the pan I used this time, a long, narrow one, or the alternate option of a tube pan. When using the latter, start checking for doneness at the 50-minute mark.
FOR THE BREAD
Butter for greasing the pan
4 bananas, ripe but firm
1/2 cup | 65 g walnut pieces
1/2 cup | 105 g dark brown sugar, packed
1/3 cup | 80 ml pure maple syrup, grade B is my preference
1/3 cup | 80 ml extra-virgin olive oil
2 eggs
1 teaspoon vanilla extract
3/4 cup | 95 g all-purpose flour
3/4 cup | 105 g whole-wheat flour
1/2 cup | 50 g rolled oats
3 to 4 tablespoons mixed seeds (I used sunflower, hemp hearts and sesame)
1 teaspoon baking soda
1 teaspoon medium-grained kosher salt
1/4 teaspoon ground cinnamon
1/4 teaspoon ground ginger
1/2 cup | 120 ml sour cream or thick, plain yogurt (not nonfat)
4 ounces | 115 g bittersweet chocolate, chopped
FOR THE TOPPING
1 tablespoon rolled oats
2 tablespoons mixed seeds
1 1/2 tablespoons flour (all-purpose or whole wheat)
1/4 teaspoon ground cinnamon
1 1/2 teaspoons extra-virgin olive oil (plus extra if needed)
1 banana, ripe but firm
METHOD
Preheat an oven to 350°F | 175°C with a rack in the lower third. Grease a 14-by-4.5-inch loaf pan with butter. Line with parchment paper, with long sides overhanging. Butter the parchment. Alternatively, butter and flour a standard tube pan, knocking out excess.
Line a baking sheet with parchment paper, then place the 4 bananas, whole and unpeeled, on top. Bake until the skin is deeply roasted on both sides, but not split, 20 to 30 minutes. Flip once during baking, and add the walnuts to the tray for the last 10 minutes of roasting (if there's a lot of liquid from the bananas, give the nuts their own tray). Remove the bananas to a bowl to collect their juices. Chop the walnuts and set aside.
Once the bananas have cooled a little, remove the peels and leave the fruit in the bowl. Mash to a pulp with the brown sugar. Beat in the maple syrup, olive oil, followed by the eggs, one at a time, mixing well after each. Stir in the vanilla. Sprinkle the flours, oats, baking soda, salt, cinnamon, and ginger on top of the wet ingredients. Fold to almost combine, then spoon in the sour cream. Give a few more turns, then gently incorporate the chocolate and walnuts. Scape the batter into the prepared pan.
In a small bowl, stir together the oats, seeds, flour, cinnamon, and olive oil until it clumps. Honestly, I do this with my fingers, and scrunch it together. Peel and slice the banana into thirds lengthwise. Scatter the streusel over the batter, then arrange the banana on top. Bake in the preheated oven until the bread is golden and puffed, and a cake tester inserted in the centre comes out clean of batter (chocolate doesn't count), 60 to 70 minutes. Cool on a wire rack 10 minutes, then use the parchment to lift the loaf onto the rack to cool completely.
Makes 1 loaf.