Cream the butter and sugar until light and fluffy, this may take a while.
Stir the flour and baking powder into the creamed mixture.
Add the eggs and combine well until smooth.
Combine the cocoa and boiling water to create a smooth slurry, then add to the mixture. Stir well to get a consistent chocolate color.
Stir in the dark chocolate either as buds or if bought as a block, broken small pieces.
Preheat the Dutch oven, or camp oven to 180 degrees C (355 degrees F).
Grease or line with parchment paper the Dutch oven or a cake tin then add the cake batter.
Bake the cake for about 20 minutes, or until cooked through.
In a bowl placed over a simmering pot of water add the dark chocolate, icing sugar, butter, and milk. Continue to heat and stir until the butter and chocolate have melted and everything is well combined.
Cut the still warm cake into portion serves then drizzle with the hot chocolate sauce.Warning: This is a very chocolaty and sweet dessert so you don’t need very large portion sizes, and it may be good to accompany with some cream or similar to pull back the sweetness a little.