Sous vide, or cooking in a waterbath, is a lovely method for cooking rhubarb, as it ensures that the stems retain their wonderful flavour and nutrients as well as their shape. For this reason, bear in mind that you will not need to add as many additional flavourings as you would with other cooking methods.
Preheat the sous vide machine to 61˚C
Wash and cut the rhubarb into batons of about 10cm long
Place the rhubarb batons in an even layer into a bag with sugar, water and any other flavourings and tightly seal under vacuum. You can add liquid to the bag, but be aware that rhubarb releases natural juices as it begins to cook so only a few tablespoons are needed
Add the bag to the water bath and leave to cook for 45 minutes - you can leave it for longer if you want the rhubarb to break down further. To check if the rhubarb is cooked, give the bag a gentle squeeze (wrap your hand in a tea towel first as it will be hot) – the rhubarb should be soft to the touch