Separate the yolks from the whites of five large eggs, keeping the egg whites for later use.
In a bowl, whisk the egg yolks with 50g of sugar until pale and slightly fluffy, then set aside.
In a pan, heat together 425ml of double cream and 100ml of whole milk.
Infuse the milk and cream with 3 heaped tsp of Earl Grey tea on medium to low heat, stirring occasionally until it comes almost to a boil.
Slowly pour the infused cream mixture onto the egg yolk mixture while whisking continuously to avoid scrambling the eggs.
Strain the mixture through a sieve to remove the tea leaves and foam.
Add 1 tsp of vanilla extract and stir gently through the custard.
Divide the mixture into 4 ramekins and place them in a bain-marie, covering with a tray.