Heat the oven to 180C/160C fan/gas 4.
Sit four 175ml ramekins in a deep roasting tin at least 7.5cm deep.
Pour the large and small cartons of double cream into a medium pan with the milk.
Put the egg yolks and sugar in a mixing bowl and whisk for 1 min with an electric hand whisk until paler in colour and a bit fluffy.
Pour the hot cream into the beaten egg yolks, stirring with a wire whisk as you do so, and scraping out the seeds from the pan.
Pour in enough hot water into the roasting tin to come about 1.5cm up the sides of the ramekins.
Put them in the oven and lay a baking sheet over the top of the tin so it sits well above the ramekins and completely covers them, but not the whole tin, leaving a small gap at one side to allow air to circulate.
Bake for 30-35 mins until the mixture is softly set.
When ready to serve, wipe round the top edge of the dishes, sprinkle 1½ tsp of caster sugar over each ramekin and spread it out with the back of a spoon to completely cover.
Spray with a little water using a fine spray to just dampen the sugar – then use a blow torch to caramelise it.