Preheat oven to 160C fan-forced. Line or grease a square cake tin.
Whisk sweet potato, sugar, oil and egg together.
Add flour, baking powder and cacao and mix together.
Gently fold in chocolate.
Pour batter into prepared cake tin and bake for 12-15 minutes, or until just cooked through.
Tips & Tricks
Mashed pumpkin works beautifully in these in place of sweet potato, although you may need to add an extra tablespoon or so of flour if the pumpkin is quite wet.You can use either milk or dark chocolate for these, depending on your preference.You can substitute 1/2 cup loosely packed brown sugar for the rapadura if you prefer.These freeze really well to pop in lunchboxes as a treat.