Mix butter and flour in a food mixer until breadcrumbs form, then add egg to create a dough.
Wrap dough in cling film and chill in the fridge for 30 minutes.
Preheat your oven to 160°C.
Roll the pastry on a floured surface to 3mm thickness.
Line a 23cm tin with pastry, spread jam on the base, and chill for 10 minutes.
Beat butter, vanilla seeds, and sugar together until pale and fluffy.
Beat in eggs one at a time, then carefully fold in the ground almonds by hand.
Spread almond mixture over the jam and decorate with blanched almonds in circles.
Bake for 35 to 40 minutes until risen and pale golden-brown.
Boil milk, cream, and the reserved vanilla pod in a saucepan.
Whisk egg yolks and sugar together in a separate bowl.
Pour boiling milk onto eggs while whisking, then cook over gentle heat until thickened.
Strain the custard into a clean pan and keep warm.
Serve tart wedges with plenty of warm custard.