Prepare the shortcrust pastry the day before or at least 2 to 4 hours before using it.
Put the flour in a large bowl or mixing bowl, add the salt and sugar, and mix. You can prepare the shortcrust pastry in a food processor.
Add the butter cut into small cubes and, using your fingertips, rub it into the mixture until it resembles coarse sand. The mixture should resemble coarse sand or semolina.
Whisk the egg yolk with the water and pour over the sandy mixture. Mix to bring the dough together, but do not knead.
Pour onto a work surface and 'fraise' the dough (also called 'fraser') with the palm of your hand against the work surface. This action helps to homogenize and smooth the dough without making it elastic.
You need to push the dough forward, flattening it with the palm of your hand, bring it back, and push it again.
Do this 2 to 3 times and gather into a ball.
Flatten it slightly and wrap it in plastic wrap. Refrigerate for at least 2 to 4 hours before using.
Take the shortcrust pastry out of the refrigerator and let it soften slightly before rolling it out to about 4 mm thick. The dough should remain quite firm. Lightly flour (dust with flour) the work surface to prevent sticking.
Cut 7.5 cm discs from the rolled-out dough.
Place these discs on a baking sheet and refrigerate.