1. Preheat the oven to 200°C, gas mark 6. Make the crème pâtissière by whisking together the egg yolks, sugar and cornflour in a heatproof bowl. Pour the milk into a saucepan, add the vanilla pod and seeds and bring to a simmer. Remove from the heat, strain through a sieve onto the egg mixture and whisk to combine. Return to the pan and set over a medium heat. Bring to the boil and cook for 2 minutes, whisking constantly. Transfer to a bowl, press a sheet of clingfilm onto the surface (to prevent a skin from forming) and leave to cool.
2. Roll out the pastry and cut 8 x 17cm circles. Use these to line 8 x 12cm loose-bottomed flan cases. Line with baking parchment and baking beans and bake blind for 10 minutes. Remove the paper and beans and bake for 5-7 minutes more until golden. Leave to cool.
3. Once the crème pâtissière has cooled completely, beat in the mascarpone then spoon or pipe the mixture into the pastry cases and top with the berries.
4. Heat the jam in a small saucepan with 2 tbsp water. Pass through a sieve then use a pastry brush to paint the glaze onto the fruit. Transfer to the fridge to chill for 1 hour before serving.