Ultimate rhubarb and custard tart

Method

1. First, make the pastry. Mix the icing sugar and flour in a medium bowl. Rub in the butter until the mixture resembles fine breadcrumbs (use your fingers or a food processor). Add the egg and iced water, then mix to combine. Tip out the dough onto your worktop and bring it together with your hands, kneading lightly until smooth. Wrap the pastry, then rest in the fridge for 30 minutes or more (see Make Ahead)
2. Put the rhubarb in a mixing bowl with the 50g sugar, crushed star anise and scraped seeds from half the vanilla pod. Tumble the rhubarb around the bowl to coat, then leave to macerate while you bake the pastry case – mix now and then.
3. Heat the oven to 180°C/160°C fan/ gas 4. On a lightly floured surface, roll out the pastry to a 3mm thickness. Line the tart tin with the pastry, pushing it into the edges and leaving an overhang. Chill for 30 minutes in the fridge.
4. Line the pastry case with baking paper and ceramic baking beans or uncooked rice. Blind bake the tart case for 25 minutes, then remove the baking beans/rice, trim the overhang and return the tart case to the oven for 10 minutes or until the base is just starting to colour. Remove and set aside, then turn the oven down to 140°C/120°C fan/gas 1.
5. Spread out the rhubarb on a roasting tray, then bake for 15–20 minutes until just tender but still holding its shape completely. Leave to cool (see Make Ahead).
6. For the custard, heat the milk and cream in a pan over a medium heat with the remaining scraped vanilla seeds and the pod halves until the mixture is very hot but not boiling.
7. Meanwhile, using a balloon whisk, whisk the eggs, yolks, sugar and cornflour in a large bowl. Pour the hot cream into the egg mixture, whisking well, then pour the custard mixture into a clean heavy-based pan and put it over a low to low-medium heat. Cook, stirring regularly, until thick. Don’t let it get too hot. Pass the custard through a fine sieve into a bowl (to remove the vanilla pod and any lumps; discard the contents of the sieve) and set aside – see Make Ahead. Turn the oven to 180°C/160°C fan/gas 4.
8. Use a fork to lift half the rhubarb from the roasting dish and arrange it on the bottom of the cooked pastry case. It’s important to leave any juice behind or it will thin the custard – but save the juice to serve. Pour the thickened custard over the rhubarb and arrange the remaining pieces of rhubarb on top. Let them sink into the custard a bit.
9. Put the tart in the oven and bake for 35 minutes or until the custard is set with a wobble. Set aside to cool, then serve with any cooking juices.