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 for ramekins and 50 minutes for 1L dish 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.