Place the flour, egg yolk, salt, sugar and butter in the bowl of a food processor and pulse until the mixture resembles coarse breadcrumbs. Alternatively, rub in the butter by hand or using a pastry cutter.
Add the water, a few drops at a time and pulse a couple of times until the mixture starts coming together. Tip the mixture onto a clean surface and bring into a dough ball.
Slightly press the ball into a disc, wrap in cling film and refrigerate for at least 1 hour to overnight. Take the dough out of the fridge 10 mins prior to rolling.
Preheat the oven to 180°C .
Cut the dough into 3 pieces, if making 3 small tarts and roll each piece into a ball. Skip this step and proceed to rolling if making a large tart. Roll balls between 2 pieces of parchment into a 4 mm thick circle and gently press into tart shell case. Trim off any excess.
Line the tarts with a a piece of crumpled baking/parchment paper. Fill with baking beans or small beans or rice.
Bake the small tarts with the baking beans for 12 minutes (18 minutes for large tart), remove the baking paper filled with the beans and bake for another 8 minutes, or until lightly golden brown (10 minutes for large tart).
Allow to cool for 10 minutes before removing the tarts from the case and let cool completely before adding the filling.