Lightly butter two ramekins and set aside.
In the top of a double boiler place the semi-sweet and unsweetened chocolates and cook, stirring occasionally, until melted. Remove from heat and stir in the butter and sugar until smooth. Add the egg, flour, baking powder and cocoa. With an electric mixer, beat at medium-high speed until pale and very thick, about 5 minutes. Place mixture in prepared ramekins, filling about half-full. Cover with plastic wrap and freeze for at least 3 hours.
When ready to serve, preheat oven to 375?F. Place ramekins on the middle shelf in the oven and bake until edges are set but centers are still shiny, about 10 or 11 minutes. Invert pudding cakes onto plates and serve immediately, garnished with whipped cream or ice cream. (Desserts may also be served directly from ramekins.)
Yield: 2 servings