Ingredients
Cooking oil spray, to grease
2 x whole small sweet potatoes, about 150g each
180g peeled very ripe bananas
100ml extra virgin olive oil
50g natural yoghurt
1 free-range egg
1⁄2 tsp fine salt
120g plain flour
80g wholemeal plain flour
3 tsp baking powder
120g caster sugar
1⁄2 ripe banana, sliced lengthways
Method
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Preheat oven to 170°C fan-forced (190oC conventional). Grease a 24 x 13 x 6cm loaf tin with cooking oil. Line base and side with baking paper, allowing long edges to overhang by 5cm.
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Place unpeeled sweet potatoes on an oven tray. Bake for 55 mins or until very tender. Set aside to cool for 30 minutes or until room temperature.
Cut 1 potato in half and scoop out flesh, transfer to a large bowl. Reserve remaining potato for garnish.
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Combine banana and potato until a smooth puree forms.
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Whisk oil, yoghurt, egg and salt in a separate large bowl until just combined.
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Sift flours and baking powder into a separate large bowl, returning husks from wholemeal flour back to flour mixture.
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Put banana and sweet potato mixture in the bowl of an electric mixer, add sugar and beat with a paddle attachment on medium
speed until incorporated. Add oil mixture, beat on low speed until combined. Add flour mixture and beat for 2 minutes or until combined.
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Spoon the batter into prepared tin and smooth surface.
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Cut remaining sweet potato in half. Set aside one half for another use. Peel remaining half and thinly slice into bite-size pieces.
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Top cake batter with sliced banana and sweet potato pieces. Bake for 55 minutes or until cooked when tested with a skewer. Set aside to cool in tin for 20 minutes, then turn out on a wire rack to cool completely. Transfer to a platter and serve.