Preheat the oven to 400°F. Butter 4 individual soufflé dishes, about 8 ounces each. Lightly dust the bottom and sides of the dishes with sugar. Melt the chocolate over barely simmering water; set aside to cool.

In a large bowl, beat the egg whites until foamy. Add the salt and cream of tartar, and beat until soft peaks form. Gradually add 2 tablespoons of the sugar, beating until stiff, glossy peaks form. In a medium bowl, beat the egg yolks until thick and pale in color. Beat in the remaining 4 tablespoons sugar. Stir in the vanilla or framboise and the melted chocolate. Fold one-fourth of the beaten egg whites into the chocolate mixture. Fold this mixture into the remaining egg whites. Spoon the soufflé mixture into the prepared dishes. Bake for 10 minutes, or until set and golden brown.

Meanwhile, make the sauce: Purée the raspberries in a blender and push them through a sieve, discarding the seeds. Sweeten to taste. Pour the sauce into a pitcher. Slash each soufflé with a spoon and pour in a little sauce.