Combine the heavy cream and whole milk in a saucepan. Warm until hot and just beginning to simmer, but do not boil.

Remove from the heat, stir in the Thai tea mix, and steep for 15 minutes.

Strain the infused cream through a fine-mesh sieve.

Preheat the oven to 300°F (150°C) and place four ramekins in a deep baking dish.

Whisk the egg yolks, sugar, vanilla, and salt until smooth.

Slowly pour the hot tea cream into the yolk mixture while whisking constantly.

Strain the custard again and divide it between the ramekins.

Pour hot water into the baking dish until it reaches halfway up the ramekins.

Bake for 35 to 40 minutes, until the edges are set and the centers still wobble gently.

Cool, refrigerate for at least 2 hours, sprinkle with sugar, and torch until the topping becomes deep amber and crisp.