Preheat the oven to 180°C and grease a 22cm flan tin.
Process flour, eggs, yolks, butter, and sugar into a soft dough.
Form pastry into a disc, wrap in film, and chill for 20 minutes.
Roll pastry to fit the tin and line with parchment and beans.
Blind bake at 180°C for 15 minutes and allow to cool.
Heat milk with vanilla pod and seeds in a pan until boiling.
Whisk egg yolks and sugar until thick and pale.
Sieve hot milk into the egg mixture while stirring or whisking constantly.
Reduce oven temperature to 100°C.
Pour custard into the pastry case and bake for 45 minutes.
Dissolve 50g sugar in 150ml water and bring to a boil with tea bags.
Add prunes to the liquid and soak until tea bags are removed.
Cool the tart and reheat the prunes to serve alongside slices.