Roll pastry on a lightly floured bench to 2 millimetres thick. Line four 10 centimetre-wide tart shells and rest for a minimum of 30 minutes. Preheat oven to 160C.

To make lavender pastry cream, bring milk and lavender to the boil. Whisk together yolks, castor sugar and flour.

Pour over hot milk, combine well and return to the saucepan. Cook over a medium heat, stirring continually until thick and shiny, about 20 minutes. Pass immediately through a fine strainer, discarding lavender. Cover with cling film to prevent a skin forming and chill in the fridge.

Blind-bake tart shells until golden and cooked through, about 25 minutes. Remove to a cooling rack. Turn oven to 200C. Cut rhubarb to 8cm lengths. Place on a baking tray, sprinkle with raw sugar and bake for 10 minutes.

Fold cream through lavender mixture, spoon into pastry shells and top with rhubarb just before serving.