- Preheat oven to 400F. Grease and flour a 9-inch cake pan or sandwich tin.
- Melt the chocolate in a metal mixing bowl over a saucepan of hot simmering water. Add the butter and stir well to mix the two ingredients completely.
- Put the eggs and the sugar in a large mixing bowl and beat with a kitchen mixer or whisk until the mixture turns pale and doubles in volume. Add the flour, a tablespoon at a time, and the baking powder; mix well.
- Add the chocolate mixture to the cake mixture and mix well. Pour into the prepared pan and bake 30-40 minutes, or until a knife inserted into the center comes out clean.
- Allow the cake to cool for approximately 15 minutes before unmolding.
- Heat a small sauce pan over medium heat. Add the sugar and melt until all of the sugar is dissolved, stirring constantly so as not to burn the sugar.
- Add the butter and stir constantly until the butter is fully melted and incorporated.
- Reduce heat to low, and add the heavy cream. Stir until fully incorporated, and the sauce is smooth and creamy.
Serve slices of cake with the caramel sauce poured/drizzled over the top.