For the pastry, combine the flour, butter, sugar, yeast and salt in a large bowl or the bowl of an electric mixer fitted with the dough hook. Pour in the water and knead for 10 minutes until the dough is smooth. Cover the bowl and leave to rest for 1 hour or overnight in the fridge.⏱ 70 min
For the sugar-crumb topping, rub the butter into the flour and sugar until the mixture is crumbly, then keep in the fridge until needed.
Make the custard according to the instructions below.
While the custard cools, preheat the oven to 180°C (350°F). Do not use the fan setting.
When the pastry has risen, knock out the air and roll out the pastry as thin as you can, then lay it over the greased tin. Press it into the base and cut away the excess pastry. Pierce the base all over with a fork, then spoon the custard into the tart. Get the sugar crumb topping out of the fridge and sprinkle it over the custard.
Bake in the middle of the oven for 30–35 minutes. Set aside to cool completely and serve cold.⏱ 33 min
For the custard, have a large, shallow ovenproof dish ready. Whisk the egg yolks, sugar and custard powder until creamy. In French culinary terms, you've now made a ruban (ribbon).
In a large saucepan, warm the milk and cream with the seeds of the vanilla bean. Remove from the heat and strain the milk if you want to get rid of the black vanilla seeds, or leave them in and show the world you used the real stuff. Add a tablespoon of the warm milk to the ruban and whisk well, then add the ruban to the warm milk, whisking constantly. Return the pan to the stove over low heat and whisk until the custard thickens, turning off the heat as soon as the mixture begins to give more resistance to whisking.
Immediately pour the hot custard into the cold ovenproof dish, then cover the top of the custard (not the dish) with a sheet of plastic wrap. The plastic wrap prevents the custard from forming a skin. Let the custard cool.