Make the custard a day ahead and broil the topping at the last minute.
2 1/2 cups whipping cream, divided
5 (1-ounce) semisweet chocolate squares
6 egg yolks
1/2 cup sugar
1 teaspoon vanilla extract
6 tablespoons light brown sugar
How to Make It
Cook 1/2 cup whipping cream and chocolate in a heavy saucepan over low heat, stirring constantly, until chocolate melts and mixture is smooth. Pour into a large bowl.
Whisk together remaining 2 cups whipping cream, yolks, sugar, and vanilla until sugar dissolves and mixture is smooth. Whisk 1 cup egg mixture into chocolate mixture until smooth. Cover and chill remaining egg mixture. Pour chocolate mixture evenly into 6 (8-ounce) custard cups; place cups in a 13- x 9-inch pan. Add hot water to pan to a depth of 1/2 inch.
Bake at 325° for 30 minutes or until almost set. (Center will be soft.) Slowly pour remaining egg mixture evenly over custards, and bake 20 to 25 more minutes or until set. Cool custards in water in pan on a wire rack. Remove from pan; cover and chill at least 8 hours.
Sprinkle each custard with 1 tablespoon brown sugar; place custards in a pan.
Broil 5 1/2 inches from heat (with electric oven door partially open) until sugar melts (about 2 minutes). Let stand 5 minutes to allow sugar to harden.