Pre-heat your oven to 170°C, spray an 8 inch square cake tin with low-calorie cooking spray and line with non-stick baking paper.
Place the reduced fat spread, granulated sweetener, baking powder, self raising flour, eggs, cocoa, orange zest and chocolate orange syrup into a large mixing bowl and mix.
Pour into the cake tin and sprinkle over the chocolate orange chunks. Place in the oven for 16 minutes until slightly risen and set.
Leave to cool in the tin for a few minutes and then transfer to a wire rack. Cut into 16 squares and serve.