Shape dough into a 4 in x 4 in square and wrap with plastic.

Transfer dough to a lightly floured work surface and continue to knead until dough is more or less smooth, about 1 to 2 minutes. Shape dough into a 6 in x 6 in square and wrap with plastic.

Place both dough in the refrigerator for 30 minutes. In the meantime, grease 16 mini egg tart molds (2.75 inch).

After 30 minutes, remove both dough from the refrigerator. Roll out the water dough into a 10 in x 10 in square. Place the oil dough in the center and cut out the corners of the water dough about 2 inches deep.

Wrap the left and right side of the water dough over the oil dough to meet in the center. Then, wrap the top and bottom of the water dough over the oil dough to meet in the center. Rotate the dough 90⁰ and flip it over with seams facing down. Roll it out into a rectangle of about 6 in x 12 in.

Flip the dough over with seams facing up. Fold the bottom ⅓ of dough over the middle. Then, fold the top ⅓ over the middle. Rotate 90⁰ and flip dough over with seams facing down. Roll it out into a rectangle of about 6 in x 12 in.

Flip the dough over with seams facing up. Fold the bottom ⅓ of dough over the middle. Then, fold the top ⅓ over the middle. Wrap with plastic and let dough rest in the refrigerator for 15 minutes.

After 15 minutes, remove dough from refrigerator and cut it in half crosswise.

Roll one portion of the dough out into roughly 10 in x 17 in rectangle and about 1/8 in thick. Cut out 8 pieces of dough with a 3.75 inch round scalloped cookie cutter.

Take a piece of the dough and gently press it into a greased mini egg tart mold. The dough should extend slightly above the rim of the mold. Repeat with the remaining 7 pieces of dough.

Do the same for the other half portion of dough.

Place mini egg tart molds lined with dough onto 2 baking trays and let them rest in the refrigerator while you prepare the egg custard filling.

Combine boiling water and sugar in a small measuring cup. Stir until sugar dissolves completely. Set aside and allow syrup to cool.

Place eggs, evaporated milk, and vanilla extract in a large measuring cup. Whisk the egg mixture until combined. Pour cooled syrup into the egg mixture. Whisk to combine.

Strain egg custard mixture through a fine sieve.

Preheat oven to 400⁰F/200⁰C.

Remove mini egg tart molds lined with dough from the refrigerator. Carefully fill each egg tart to about ¼ inch from the top edge of the dough. Pierce any bubbles that may have formed on the surface of the egg custard with a toothpick.

Carefully transfer baking trays with filled mini egg tarts to preheated oven. Bake for 10 minutes at 400⁰F/200⁰C. Reduce temperature to 350⁰F/180⁰C and continue to bake for another 15 to 17 minutes until egg custard has set. If you see egg custard starting to bubble or puff up, rotate the baking tray.

When baking is complete, turn off the oven and leave oven door open. Let the egg tarts sit in the opened oven for 5 minutes to allow the egg custard to deflate gently. After 5 minutes, remove baking trays from the oven.

Allow mini egg tarts to cool before removing the mold and transferring them into cupcake liners.