Set oven control to broil. With paper towel, carefully blot any surface liquid from top of custard. Spoon brown sugar into fine strainer. With fingers or back of spoon, press brown sugar through strainer evenly over top of custard. Broil 6 to 8 inches from heat 30 to 60 seconds, rotating or moving dish if sugar is melting unevenly, until brown sugar is melted and bubbly (watch carefully, as topping burns easily). Cool 2 minutes to harden sugar. Serve immediately.