Line long sides and bottom of 8-1/2 x 4-1/2-inch loaf pan with waxed paper, with a little overhang along both long sides. Spread ice cream evenly over bottom of pan and up the long sides, forming a U-shape. Place in freezer until firm.
Meanwhile, stir together powdered egg whites and 3 tablespoons water in medium-size bowl to dissolve whites. Let stand.
Puree raspberries, jam, 2 tablespoons sugar and lemon juice in blender or food processor. Force through sieve with rubber spatula to remove seeds.
Beat egg white mixture until soft peaks form. Gradually add the remaining 2 tablespoons sugar; beat until stiff peaks form.
With same beaters, beat heavy cream in large bowl until soft peaks form. Fold raspberry mixture, then egg whites into beaten cream. Spoon into ice cream-lined loaf pan. Cover with plastic wrap. Freeze overnight. To serve, unmold, and slice. Garnish with berries, if desired.