Stir together cream and 1 tablespoon sugar; heat through in a bowl over a saucepan of boiling water. Whisk egg yolks into the cream; pour into a large shallow dish and stand in a roasting tin filled with 2.5cm boiling water.
Bake in the preheated oven until set, about 40 minutes; leave to cool overnight.
Sprinkle 75g caster sugar evenly over top of custard. Place under a very hot grill until sugar has melted and turned golden, about 2 minutes.