For the rhubarb, place the water, sugar, ginger, and the half vanilla bean in a medium saucepan and bring to a boil over medium-high heat. Reduce the heat so the syrup is boiling, whisking from time to time, until the sugar is dissolved. Add the rhubarb, stir gently so it is mixed with the syrup (it may seem there is too much rhubarb – don’t worry, it’s just fine), and return the syrup to a low boil. Shake the pan and watch the rhubarb as it cooks and stir if necessary. Depending on its texture, the rhubarb will cook in about 1-1/2 minutes, though it can take up to 5 minutes. You can tell because it begins to turn color and if you touch a piece, it will begin to soften. Remove from the heat and leave the rhubarb in the syrup to cool.