In a bowl, combine the flour, salt, and 1 tablespoon sugar.
Add the butter and break it up roughly with your fingers, making sure to keep visible little chunks of butter in the dough
The mixture will resemble like sand
Add 2 tablespoons of cold water and bring the dough together. Add a tiny bit more water if necessary, but not too much, as this will make your pastry tough.
Cover the dough and refrigerate for 20 minutes
Turn out the dough onto a lightly floured board, knead gently, and form into a neat rectangle
Roll the dough away from you (not back and forth), forming a long rectangle (about 8×20 inches). Try to keep the edges straight
Fold the same way as before, cover, and chill for 30 minutes. At this point, the dough is essentially done.
Flecks of butter should still be visible in the dough.
Fold the top third of the dough down to the center, then the bottom third up and over that. Give the dough a quarter turn (left or right) and roll out again to three times the length.
While the dough is resting, make the filling. Dissolve the 1/2 cup of sugar into the hot water, and allow to cool to room temperature.
Thoroughly whisk eggs and evaporated milk together and then whisk in the sugar water and vanilla.
We don't want bubbles that inevitably form from whisking. Strain through a very fine mesh strainer–this step is extremely important to getting a smooth, glassy egg tart.
Preheat oven to 400 degrees F/200 degrees C and position a rack in the lower third of your oven. Roll out the dough and cut circles to fit your tins
Once filled, immediately put into the oven. Very carefully transfer the muffin tray to your preheated oven and bake for 15 minutes.
Reduce the temperature to 350 degrees F/180 degrees C and bake another 10-12 minutes, until filling is just set (if a toothpick can stand up in it, it’s done).
If you see the pastry/custard starting to puff up a bit too much, your oven is a little too hot. But don’t worry, if you catch it early enough, open the oven slightly, and they won’t crack.
When you take them out, they’ll settle back down again.
You can let the tarts cool for a couple minutes and enjoy them while they’re still hot.