Frozen Plum Souffles with Cardamom-Plum Sauce

For souffles: Cut four 14x6-inch foil strips. Fold each in half lengthwise. Wrap 1 foil strip around each of four 3/4-cup soufflé dishes, forming collars that extend from base to above rim. Fold and crimp ends to secure. Combine chopped plums and 1/4 cup sugar in heavy medium saucepan. Simmer over medium heat until mixture turns bright red and is reduced to 1 1/2 cups, stirring often, about 8 minutes. Transfer mixture to processor; puree until smooth. Cover; chill until cold. Whisk yolks, corn syrup, butter and 1/4 cup sugar in medium metal bowl. Set bowl over saucepan of simmering water (do not allow bottom of bowl to touch water); whisk constantly until candy thermometer registers 170 °F, about 5 minutes. Remove bowl from over water. Mix in cardamom. Using electric mixer, beat egg mixture until cool and thick, about 5 minutes. Beat cream, vanilla and 1/4 cup sugar in large bowl until stiff peaks form. Add plum puree to cream; fold together. Fold in egg mixture. Spoon mixture into soufflé dishes, dividing equally (mixture will extend above rim of dishes). Cover with plastic; freeze overnight or up to 1 week. For sauce: Combine chopped plums and sugar in heavy medium saucepan. Simmer over medium heat until mixture turns bright red and is reduced to 1 1/3 cups, stirring often, about 10 minutes. Mix in 6 tablespoons water and cardamom. Transfer to processor and puree. Transfer sauce to bowl. Cover; chill until cold, at least 3 hours or overnight. Carefully remove foil from soufflés. Drizzle some sauce over each. Top with plum slices. Serve with remaining sauce.