Preheat oven to 200C.

Spray with cooking spray and line a 24cm cake tin. Make sure the lining reaches up over the sides of the tin giving you handles to remove the brown when cooked.

In a stand mixer, cream the sugar and eggs until light and fluffy. Add the sweet potato and vanilla extract and blend well.

In a small saucepan, melt the butter without boiling and then add the dark chocolate pieces and stir until melted over a very low heat.

Add the chocolate mixture to the sweet potato mixture and blend well.

Sift the chocolate,  and cocoa together and then add to the sweet potato mixture along with the salt and blend well without over beating. 

Add the choc chips to the mixture and stir through.

Pour the mixture into the lined cake tin and place in the oven and cook for 6 – 8mins until the top has cooked then reduce temperature to 180C and cook for a further 12 – 15mins until cooked though. A skewer placed into the center should come out just clean. Don’t over cook or the center will loose its fudginess.

Remove from the oven and allow to cool slightly before using the baking paper to lift the cooked brownie from the tin.

Serve warm or cool.