Combine first 4 ingredients in a large saucepan. Cook over low heat, stirring constantly, until chocolate melts and mixture is smooth (do not boil). Remove from heat. Stir in flavorings.
Gradually stir about one-fourth of hot whipping cream mixture into beaten egg yolks; add to remaining hot whipping cream mixture, stirring constantly.
Pour custard mixture evenly into 9 (4-ounce) ramekins. Place ramekins in a large roasting pan or 2 (9") pans; add hot water to pan(s) to depth of 1". Bake, covered, at 325° for 40 minutes. Remove ramekins from pan(s); cool slightly on wire racks. Cover and chill up to 24 hours.
Place ramekins on a baking sheet. Sprinkle each with 1 tablespoon brown sugar. Broil 3" from heat just until sugar melts. Cool on wire racks 5 minutes to allow sugar to harden.