Melt the chocolate with the butter in the top of a double boiler; set aside to cool. In an electric mixer with a paddle attachment (or by hand, with a spoon), mix the sugar and eggs until lightened in color, about 1 minute. Pour in the cooled chocolate-butter mixture, then beat or stir in the 1/2 cup cream, vanilla, and salt. Beat well, scraping down the sides of the bowl as you go. Add the flour and mix just until blended. Divide the mixture between 4 (6-ounce) oven-proof cappuccino cups. (They should be filled to 1/4-inch below the rim of the cup.) Put them on a baking sheet and bake for 30 to 35 minutes, just until the tops begin to crack. Do not over bake (the top should be crisp but the interior soft). Let them cool for about 15 minutes while you make the whipped cream.
Dissolve the espresso powder in the remaining 1 cup of heavy cream, then whip the cream until it forms soft peaks. Put a dollop of the flavored whipped cream on each warm "cappuccino" and garnish with a dusting of cocoa. Serve warm.