Preheat oven to 210C/410F and have your pie tins ready. Cut out rounds of shortcrust pastry for the bases as large as your pie tins. Dock holes at the bottom and bake for 15 minutes.
In the meantime, place the rhubarb and water into a saucepan and heat. Allow to soften, then add the sugar and vanilla. Taste for sweetness and strain and cool the rhubarb.
Fill the pastry bases with the rhubarb. Cut out fluted rounds in the shortcrust pastry for the top. Secure to the base brushing with the egg wash mixture.
Halve the cherries and cut out small rounds that are big enough to wrap around the cherry. Cut these in half to form half moons or 'eyelids' and gently cut a little line for a double eyelid.
Brush the tops of the pies with egg wash, place half cherry and gently press the 'eyelid' into place. Brush egg wash on the eyelid and bake for 15 minutes. When cool, draw a white line under the cherry eye and a tiny dot.
