About this recipe:Homemade pastry and custard from scratch makes this rhubarb tart truly scrumptious. It does take some effort but you can get ahead by cooking the pastry, or rhubarb and fresh custard ahead of time. Just before serving, you can dust the top with caster sugar and caramelise it under the grill or by using a cooks blowtorch.
Preheat the oven to 200 degrees C / Gas mark 5. Lightly butter a 28cm loose-bottomed fluted pastry tin.
To make the pastry: place the flour and cubes of cold butter in the bowl of a food processor and mix for 10 to 15 seconds (or rub the flour and butter together with your fingertips until it looks like breadcrumbs).
Add the sugar, beaten egg and 1 dessertspoon of water. Blend together, adding more water if necessary until it forms a dough. Roll out on a floured surface and line the fluted pastry tin. Prick the pastry base with a fork, then place in fridge while you cook the rhubarb and make the custard.
Simmer the sliced rhubarb in a covered saucepan over a moderate heat until tender. Set aside.
To make the custard: Bring the milk and a split vanilla pod to the boil. Remove from the heat and set aside to infuse.
In a large bowl, whisk caster sugar and egg yolks until pale. Whisk in plain flour.
Remove the vanilla pod from the milk and gradually whisk the warm milk into the egg yolk mixture. Pour it into a saucepan and cook, stirring, until it just comes to the boil, the simmer very gently for 2-3 minutes to cook out the floury taste. Whisk in 1/2 teaspoon of soft butter.
Bake the tart in preheated oven for 10 -12 minutes to allow the base to cook. Set it on a baking tray; spoon the cooked rhubarb evenly over the pastry base and carefully pour (or ladle) in the custard until it reaches near the top of the pastry.
Lower the oven temperature to 150 C / Gas 2. I use the bottom oven in the Aga for this. The temperature should be low enough to just set the custard in the tart - if the oven is too hot hot the tart will end up like scrambled eggs.
Cook for 45 minutes to 1 hour, or until the custard is no longer liquid and wobbles slightly when you shake it. Allow to cool a little before serving or serve cold.