Preheat oven to 175C. In a blender, blend canellini beans, dates, oil, baking powder and a pinch of salt. Once blended melt the chocolate using a water bath then add to the blender together with the cocoa powder. Blend again then add chocolate chips and walnuts and mix to combine. Pour the mixture in a greased baking tin or use baking paper. Cook in the oven for 25/30 minutes until the sides separate from the paper. Leave to sit for 10 minutes, cut into slices and enjoy!