In a large bowl, add the cold butter cut into small cubes, flour,icing sugar, and salt. Incorporate the butter in the dry ingredients using yourhands until you obtain a sand-like texture. Make a well in the center and whisk an egg inside. Incorporate it into the dough first with a fork, then kneadlightly by hand until the egg is well incorporated. Roll out the dough to a one-inch-thickrectangle. Cover well and refrigerate for at least one hour.Remove the dough from the fridge, let it sit at room temperature for 5-10 minutes until it becomes softer and easier to spread. Divide your dough in two. Add some flour on your counter to make sure that the dough will not stick to it. Roll the first half thin (3 mm), then cut a circle using the same ring you’ll bake your flan in. Put that dough circle in the freezer.Roll the second half just as thin and cut long strips, slightly taller than the height of your ring. These will be your sides—freeze them too.Butter your ring and place it on a parchment-lined baking tray. Gently line the sides with the dough strips, then place the frozen dough circle at the bottom. Press lightly. Chill everything in the fridge for at least 30 min. Cut the excess dough. Spread the dough with a rolling pin until it’s 3-5 mm thick. Watch my video showing how to line a tart.Leave the dough in the fridge for at least 30 minutes
Pastry cream
Put the vanilla pod in milk and whipping cream and let warm it up in a pot until it starts boiling. Let the vanilla pod sit in the milk for 15 minutes.In a separate bowl, mix the egg yolk with the sugar then add the cornstarch and whisk. Put 1/3 of the milk in the egg mixture. Mix well and put this back to the pot.Heat everything together while continuously stirring. Stir for 3 min after it thickens. Remove from the stove before adding butter. Mix well with a whisk and with a hand mixer if you have one.Pour in a baking dish with cling warap on top of it. Leave in the fridge for at least 30 min.
Baking
Preheat your oven at 170C(340F). Pour pastry cream onto cold pie dough. Fill up to 3/4 of the height of the pie dough. Bake for 45 min. Let the flan cool down at room temperature for 1h then in the fridge for at least 5 hours.