Preheat oven to 180°C / 350°F and roast sweet potatoes whole with skin on until completely soft in the middle
Line an 8 × 8 inch, 20 × 20 cm pan with baking paper
In a bowl, peel and mix sweet potato, peanut butter, cocoa powder and maple syrup until smooth
Fold through the dark chocolate chips
Spread evenly into the pan
Bake for 18–21 minutes, until a toothpick comes out with moist crumbs
Allow to cool before slicing, they firm up as they set
