Leave the butter and egg at room temperature. Grease the tart tin thinly with margarine and chill in the fridge. Sift the flour.
Add the salt to the butter and mix until the butter looks like mayonnaise. Add the icing sugar and mix further.
Add the beaten egg yolk in three batches and continue to beat. Add the vanilla extract.
Add the sifted flour and mix well with your spatula.
Shape the dough into a similar shape to the tart tin that you are going to use (if it's a round shape into a circle, into a square shape if it's a square). Wrap with cling film and chill in the fridge overnight (or for at least 3 hours).
Take the dough out of the fridge and microwave at 500W for 20 seconds. Sandwich the dough with 2 pieces of cling film.
Roll out the pastry dough into an even 3-mm thickness, larger than the tart tin.
Peel off the top cling film. Place the tart tin upside down and flip over by lifting up the bottom cling film.
Line the tart tin with the pastry dough, pressing all the way into the bottom edges tightly with your fingers.
Trim the excess pastry by rolling a rolling pin over the tin. Fold the excess over the sides.
Prick the base and sides with a fork to prevent from swelling. Chill the pastry in the fridge for at least 1 hour to prevent form shrinkage.
Line the tart tin with baking parchment and fill with baking beans. Bake in a pre-heated oven to 180°C for 10 minutes. Remove the parchment and baking beans and bake for a further 10 minutes.
Use this tart crust for making any sweet tart desserts.
I love the good combination of tart pastry and sweet egg custard in 'Pumpkin & Egg Pudding Tart' https://cookpad.com/en/recipes/147136-kabocha-pudding-tart