Step 1

Line the bottom of a 9 inch round cake pan with a circle of baking paper and spray the pan all over with a light coating of oil.

Step 2

Preheat the oven to 355F/180C.

Step 3

Pierce the sweet potato all over with a fork, then place on a plate or kitchen towel. Microwave on high for 6 to 8 minutes until the flesh is soft. Cut open lengthwise and scoop out the flesh. Mash it well in a medium bowl or jug (or pulse in a food processor for a few seconds). Let it cool a little.

Step 4

Combine the flour, cocoa powder, salt & baking soda in a medium bowl.

Step 5

Add the eggs, vanilla, oil and maple syrup to the sweet potato and mix well with a wooden spoon. Add to the dry ingredients and mix again until well combined.

Step 6

Pour the batter into the prepared baking pan and bake for 18 minutes or until the top is just cooked and the centre is still a bit gooey.

Step 7

Let cool for 10 minutes in the pan, then carefully turn out onto a wire rack to cool completely.

Step 8

Pulse the avocado, cocoa and maple syrup in a food processor until silky and smooth. Once the cake is completely cool, spread the frosting thickly all over the top and sides.