In a small saucepan, heat butter and chocolate until almost melted. Remove from heat and stir until smooth. Let mixture cool at room temperature.
In a small mixing bowl, beat the egg, egg yolk, and brown sugar with an electric mixer for about 3 to 4 minutes or until very light and a ribbon forms when you raise the beaters. Beat in the chocolate mixture. Fold in the flour.
Divide the chocolate batter among 4 buttered 6-ounce custard cups. Divide the 1 cup fresh raspberries on top of the batter in the custard cups.
Bake the desserts in a 450 degree F oven for 12 minutes. Sift some powdered sugar over the tops. Serve at once with sweetened whipped cream and garnish with additional berries, ice cream, and mint sprigs, if you like.