chocolate souffles

Combine first 7 ingredients in heavy medium saucepan. Stir over low heat until chocolate melts and mixture is smooth. Remove from heat; cool to lukewarm. (Chocolate base can be made 1 day ahead. Cover; chill. Stir over low heat just until lukewarm before continuing.)

Preheat oven to 350°F. Butter eight ¾-cup ramekins or custard cups and coat insides with sugar. Whisk egg yolks into lukewarm chocolate base. Using electric mixer, beat egg whites and cream of tartar in large bowl until soft peaks form. Fold whites into chocolate base in 3 additions.

Divide soufflé mixture among prepared ramekins; place on baking sheet.

Bake soufflés until puffed but still moist in center, about 15 minutes. Sift powdered sugar over soufflés and serve immediately.