Place raspberries and 1/4 cup sugar in a stainless steel bowl. Crush berries into a rough texture. Set aside for a few minutes.
Add chocolates to raspberries and place over a double boiler. Stir periodically to avoid scorching the chocolate. Keep over low heat until the chocolate has melted, 25-30 minutes. Remove from heat and set aside to cool.
Beat egg whites until they form soft peaks. Gradually add remaining 1/4 cup sugar; beat until the peaks are stiff but not dry.
Beat heavy cream until it forms stiff peaks.
Add 1/4 of the egg whites to the chocolate, stirring well to incorporate, lightening the chocolate. Fold in the cream and remaining egg whites, being certain that no white streaks remain. Keep refrigerated until used.
Ingredients
2 pints fresh raspberries
1/2 cup granulated sugar
32 ounces semisweet chocolate , chopped fine
8 ounces unsweetened chocolate , chopped fine
12 egg whites
3 cups heavy cream