In a food processor or bowl, combine the flour, sugar & cold butter together. Using your hands or using a food processor crumble the butter into the flour & sugar mixture until it resembles breadcrumb-like texture. Do not overdo it as the butter may start to melt and make the flour soggy. The breadcrumb-like texture is what you want
To this mixture add the egg yolk and mix well. The dough at this point should come together and form a rough ball. Only if the dough still feels dry add the egg white as needed
Once the dough is ready, place it on a piece of cling wrap and flatten it into a disc-like shape. Cover all around with cling wrap and let it sit in the refrigerator for half n hour
Once chilled remove it from the fridge
How to roll the Sweet Pastry Crust Dough
Place a big piece of cling on your platform. Dust some flour onto the cling wrap. Place the dough on this piece of cling wrap. Dust some more flour on the top of the dough. Place another piece of cling wrap on top of the dough (it's like a sandwich now, cling wrap-dough-cling wrap). Using a rolling pin evenly roll the dough without moving the cling wrap.
Once you have rolled it to the required size remove the top cling wrap piece and lift it carefully holding the bottom cling wrap piece (you are now transferring the rolled dough into the tart crust pan) Peel off the bottom cling wrap once you have managed to place the rolled dough onto the tart pan. Press the dough on all sides of the tart pan making sure you have clean edges
Let this tart now sit in the fridge for 20 minutes before we put it in the oven
Once chilled, remove the tart from the fridge and using a skewer prick the pie all over. Place a piece of butter paper on the top of the uncooked tart and throw in some raw beans on top of the butter paper. The weight of the beans makes sure the tart is flat even after is baked with no air pockets.
Bake this in a preheated oven for 20 mins at 175 degrees C. Remove the pie from the oven, take out the beans along with the butter paper. You can even brush some egg for a nice color. Rebake this tart crust for another 20 to 25 mins or until the edges are golden and crisp.
Once done, let cool completely before you unmould