Preheat oven to 140C.
The custard: Over medium heat, combine cream, milk, sugar, chai, vanilla bean and seeds in a saucepan and stir. Simmer for 7 minutes. Meanwhile, whisk egg yolks in a bowl to combine. Whilst whisking, slowly add the cream mixture. Strain through a fine sieve directly on to four ramekins or 1L shallow overproof dish.
Slowly bake it: Place in a roasting pan, filled with enough cold water to come to ¾ outside of the ramekins or dish. Bake for 35 minutes until just set. Remove from water, cool to room temperature, then cover and refrigerate for 3 hours.
Torch it: Scatter caster sugar over the custards and using a blowtorch, caramelise the sugar. Serve immediately.