1. Pre-heat the oven to 180°C. Grease and line a 20 x 20cm square tin.
2. Gently melt the butter and chocolate in a medium sized pan.
3. Remove from the heat and mix in the sugar, Sweet’N Low and milk until well combined.
4. Sift the flour, cocoa powder and baking powder together then stir into the chocolate mixture. Add the nuts if using.
5. Pour into the tin and bake for 12-14 minutes or until risen but still slightly soft in the center. Do not overbake.
6. Allow to cool in the tray before cutting into small squares.