Preheat the oven to 140°C/275°F/gas 1. Score the vanilla pods lengthways and scrape out the vanilla seeds with a knife or a teaspoon. Place the seeds into a saucepan, add the pods, all the cream and milk and slowly bring to the boil. Remove from the heat.
Meanwhile, get yourself a large bowl that will fit over your pan and beat together the egg yolks and sugar until light and fluffy. Remove the vanilla pods from the pan and, little by little, add the milk and cream to the egg mixture in the bowl, whisking continuously. Add 2.5cm of hot water to your dirty pan, bring to a simmer and put the bowl on top of the pan. Cook the mixture for 5 minutes over the simmering water, stirring often, until it thickens and coats the back of a spoon. Stir in a small handful of lavender flowers, but the trick is to be delicate – you only need a hint of its distinctive, strong flavour.
Remove any bubbles or froth from the mixture before dividing it between your ramekins. Stand these in a high-sided roasting tray, and fill the tray with water halfway up the ramekins. Place carefully in the preheated oven and cook for around 30 to 45 minutes or until the mixture has set but is still slightly wobbly in the centre. Allow to cool at room temperature then place in the fridge until ready.
To serve, sprinkle each crème brûlée with a tablespoon of caster sugar and some more of the lavender flowers and caramelize under a very hot grill or using the chef’s torch.