Chop your rhubarb and strawberries into bite sized pieces and add to a large mixing bowl. Add your caster sugar and mix well. Leave to sit for 1 hour, stirring occasionally.
Pre heat your oven to 180°C and line a tray with baking paper.
Cut your Jus Rol pastry sheet into an oval shape.
Drain any liquid off your fruit mixture and then add to the middle of the pastry, leaving a couple of inches gap around the outside.
Start to fold your pastry inwards, so that it covers the fruit, but leaves a large open space in the centre (the photo above shows how this should look).
Using an egg (or non dairy milk mixture for a vegan option) wash, brush the outside of your pastry, this will give it a golden look when it’s cooked.
Cook for around 30-40 minutes, covering with foil for the last 10 minutes if necessary. Serve warm and enjoy!