Preheat oven to 425°F. Butter 6 (6-ounce) custard cups or soufflé dishes. Place on baking sheet.
Microwave butter and chocolate in large microwavable bowl on HIGH 1 minute or until butter is melted. Stir with wire whisk until chocolate is completely melted. Stir in extract. Stir in 1 cup of the sugar until well blended. Whisk in eggs and yolk. Stir in flour. Pour batter into prepared custard cups.
Bake 10 to 14 minutes or until sides are firm but centers are soft. Meanwhile, beat cream and remaining 1/4 cup sugar in medium bowl with electric mixer on high speed until firm peaks form. Refrigerate whipped cream until ready to serve.
Remove molten cakes from oven. Let stand 1 minute. Carefully loosen edges with small knife. Invert cakes onto serving plates. Sprinkle with confectioners' sugar, if desired. Serve immediately with whipped cream.