Step 1

Place rhubarb, strawberry, caster sugar, lemon juice and vanilla in a saucepan over medium heat. Cook, stirring occasionally, for 10 minutes or until rhubarb is broken down and mixture is jammy. Remove 1/3 cup (80ml) liquid and place in a bowl with 1 tbs cornflour, stirring until smooth and combined. Return cornflour mixture to pan and cook jam for a further 3 minutes or until very thick. Cool completely.

Step 2

Place custard and remaining 1 tbs cornflour in a second saucepan over medium-low heat and whisk for 5 minutes or until very thick. Cool completely.

Step 3

Roll out pastry to form a rectangle around 29cm long. Using a 14cm pastry cutter (or use a small bowl as a guide), cut 8 rounds from pastry and place on 2 baking trays lined with baking paper. Divide cooled custard mixture and cooled jam among the centre of the rounds. Brush edges with egg and fold to enclose in a semi-circle, crimping the edges of the pastry. Brush tops with egg and scatter with demerara sugar. Chill for 10 minutes.

Step 4

Preheat oven to 180°C. Bake pies, swapping trays halfway, for 30 minutes or until golden. Cool slightly before serving.