Preheat oven to 180C/350F/Gas 4. Line baking tin with greaseproof paper. In a bowl over some simmering water melt butter and choc and mix until smooth. Add cherries and nuts at this period, if you are using them, and stir. In a separate bowl mix all the dry ingredients together. Then add it to the chocolate mixture. Stir together well, beat the egg and mix in until you have a silky consistency.
Pour brownie mix into your baking tray. Cook in the top of the oven for around 25 mins, don’t over cook unlike cakes if you put a skewer into it shouldn’t come out clean. You want it to be springy on the outside but slightly gooey on the inside. Allow to cool then chop it up into chunky squares.