1. Pre-heat an oven to 300ºF (150ºC). In a pan add the rhubarb, 4 tbsp of sugar and half of the vanilla seeds, and allow to stew over a low-medium heat. The rhubarb will be ready when it is cooked through and has become soft, but is still able to retain its shape.
2. In another pan, add the heavy cream, the vanilla pod and the rest of the vanilla seeds, and scald over a medium heat for 5 minutes. Be careful not to boil the cream, but heat it to the point at which the edges of the cream begin to bubble when the mixture is tilted. Then allow to cool for a further 5-10 minutes.
3. Slowly mix the egg yokes into the cooled cream and vanilla mixture, making sure that the eggs do not scramble by mixing vigourously. Mix in 2 tbsp of sugar, and then strain the mixture in order to remove the vanilla pod, and make the custard smooth.
4. Place the rhubarb and syrup mixture into the bottom of a ramekin, making sure to include some of the liquid, until it fills about 1/4 of the ramekin. The amount can be adjusted according to taste. Very slowly pour the custard mixture into the ramekin, allowing enough space for a layer of sugar to be added after cooking.
5. Cook the crème brûlée in a bain-marie by filling a baking tray with boiling water, until it reaches about half of the way up the sides of the ramekins. Carefully place the tray into the oven for 20 minutes, or until the custard has a skin on the top and has set, but still has a wobble.
6. Allow the crème brûlée to rest for 2 hours in the fridge.
7. Carefully spoon 2 tbsp of sugar on top of the crème brûlée, taking care not to put any on the sides of the ramekin, and gently distribute the sugar evenly with the back of a spoon.
8. Using a blowtorch, begin to heat up the sugar. Make sure to begin on a low temperature, and gradually increase the heat as the sugar begins to turn to caramel. When the caramel begins to form pools, allow it to cool and it will distribute itself evenly, before giving it a final torch, making sure that all the sugar on the top has become caramelized. Be careful not to burn the caramel.