HEAT oven to 425ºF.
GREASE 6 (6-oz.) custard cups or souffle dishes. Place on baking sheet.
MICROWAVE chocolate and butter in large microwaveable bowl on MEDIUM (50%) 2 min. or until butter is melted. Stir with whisk until chocolate is completely melted. Add 1-1/2 cups sugar and flour; mix well. Add whole eggs and egg yolks; beat until well blended. Pour into prepared cups.
BAKE 14 to 15 min. or until cakes are firm around the edges but still soft in the centers. Let stand 1 min. Run small knife around cakes to loosen; carefully unmold onto dessert plates. Cut in half. Serve warm topped with remaining sugar. Garnish with berries.