Preheat the oven to 150C/300F/Gas 2. Put the ramekins into a roasting tin and pour in enough hot water to come halfway up the sides of the ramekins.
Put the cream, mascarpone and vanilla seeds (or extract) in a pan and heat until almost boiling, then remove the pan from the heat and stir in the ginger until well combined.
Whisk the egg yolks and sugar together in a bowl until pale and fluffy.
Gradually add the ginger cream, whisking all the time. (I like to include the bits of ginger in the crème brûlée, but if you don’t want them, place a sieve over a measuring jug and pour the cream mixture into it to sieve out the ginger. Using a wooden spoon, push the ginger mix left in the sieve to get as much flavour as you can, then discard the ginger bits.)
Divide the cream mixture equally between the ramekins, then place them (still in the roasting tin) in the oven for about 30 minutes, or until the brûlées begin to set. They should still wobble like jelly in the very centre, but should not be too liquid, nor completely set. It is very easy to overcook these so check after 20 minutes to see how they are doing. Then check every five minutes after that as some ovens are much more powerful than others.
Remove the brûlées from the oven and from the roasting tin and leave to cool, then place in the fridge for at least one hour.
Sprinkle about one tablespoon of brown sugar evenly on the top of each brûlée, making sure the tops are completely covered. Using a cook’s blowtorch, caramelise the sugar until dark brown and crisp. A very hot grill works too. Leave to cool a little and then serve immediately.