10 cups of rhubarb
1/2 cup water
1-4 cups of sugar
Roughly chop the rhubarb. Cook in 1/2 cup water in a large pot for 30 -45 minutes. The rhubarb will break down and turn into 'stewed fruit.' Once the rhubarb has broken down, add sugar to your liking - 1 cup will give you a very tart drink, and 4 cups a very sweet drink. Pour the stewed rhubarb in to a fine sieve, and set over a large bowl. Encourage the rhubarb to strain by pressing with a ladle or large spoon. You are going to have lots of pulp left in the strainer. Save it and add it to a crumble or pie! What you want is the rhubarb syrup that has drained into the bowl. This is the concentrate for your drink. Dilute it with water to your liking - I found 1 part syrup to 8 parts water was about right.
Possible additions? Ribbons of mint, club soda, or strawberry garnishes.
I wish I had a picture - it's the most attractive, remarkable shade of pinky-purple. You could also use the syrup in cocktails. Gin, rhubarb syrup, club soda? Mmmmmmm.