Wash rhubarb stalks and chop (do not use the leaves, just the stalk). Place chopped rhubarb in a medium size saucepan.

Add water to just cover rhubarb, approximately 400ml.

Wash lemon balm and add to the rhubarb.

Cook over medium heat until hot and then turn down to simmer. Cover and cook for approximately 45 minutes or until rhubarb is tender and releasing it juices. Do not stir.

Place a sieve over a large bowl and pour rhubarb mixture into the sieve. The juices will drain through. Let sit for approximately 20 minutes and then press a spoon into the rhubarb to release more of the juices. Discard pulp.

Return the liquid to the pot and heat on low heat. Add the sugar, tasting as you add, to reach the desired level of balance between tart and sweet.

If you would like a more concentrated flavour reduce your rhubarb concentrate by cooking it a little longer for more water to evaporate. This recipe makes approximately 2 cups of rhubarb concentrate.