Preheat oven to 180°C.
Heat 1 cup water in a non stick pan. Melt butter in the microwave oven on HIGH for 1 minute.
Sieve flour, baking powder, cocoa powder into a bowl. Add grated dark chocolate and mix well. Add sugar free natura diet sugar and mix well.
Add milk and mix. Break egg and put into the bowl and mix. Add melted butter and mix well.Grease an ovenproof dish with butter and put the batter into it.
Add instant coffee powder to the hot water and mix well. Pour this over the batter in the ovenproof dish. Bake in the preheated oven for 45 minutes.Serve hot.