Mix the ground Chia seeds with water and set aside. Peel the sweet potato and cut it into small pieces. Place it in a steamer to steam for 15–20 minutes. Once the sweet potato is tender, either mash it or place it in a processor until it is smooth and free of lumps. Using the kitchen mixer beat the eggs to form peaks and set aside in a separate bowl.

Melt the chocolate over a double burner. Add the flour, cocoa, walnuts and sugar to the mixing bowl with the Chia seed paste, Chia oil and melted chocolate. Fold through the egg whites. Spread the mixture across a 30 x 20 cm baking tray lined with baking paper and bake for 20 minutes. Cut into squares and store in an airtight container.