Place the butter at room temperature for about 30 minutes and it will soften
Prepare the dough or tart shells:
Mix all-purpose flour and salt in a bowl. Stir to combine. Combine the softened butter and sugar using a whisk until creamy. Gradually add in the egg mixture and whisk until combined. It may appear separate at first but just keep whisking and it will come together
Add the flour mixture and use a rubber spatula to combine at first and then use your clean hands to knead it into a smooth dough. Flatten into a disc and wrap with a cling wrap and refrigerate for at least 30 minutes
Shape the tart shells:
Divide the dough into 9 portions (I would say roughly about 30 grams each if you want to weigh it out) and roll into round balls. Lightly dust your fingers with some flour to prevent sticking if it's an issue. Place the dough ball in the mold and then use your two thumbs to start spreading the dough from center to the side of the mold. It's better if you can mold it about 1-2 mm higher on the top edge so it's easier to release and you can fill up a bit more filling too
Place the tart shells on a baking pan and place them in the refrigerator for at least 30 minutes while you prepare the custard filling
Prepare the egg custard filling:
Preheat oven to 400 F (200 C) My oven is a conventional oven, only bottom heat, no fan. Combine hot water with sugar and stir until sugar dissolves. Let it cool down to at least warm
Whisk the eggs with evaporated milk. Add the sugar water and keep whisking. Strain this mixture to get rid of any lumps. Transfer to a jug or large measuring cup with a spout for easier pouring later
Assembling the tarts:
Pour the egg custard mixture into each tart shells, about 3/4 full (as shown in the photo above)
Place the baking sheet at the lower 3rd of the oven. Bake for about 10 minutes or until the tart shells are golden brown. Then lower the oven temperature to 350 F (180 C) and let them bake until the egg custard is set, about 10 minutes or until the egg custard is set and no longer jiggly. You can insert a toothpick into the middle of the custard to check. It should come out clean
Keep a close watch on the custard, if you see the custard started to puff up, open the oven door a little bit. The custard is done when it's no longer wobbly and when you insert a toothpick in the middle of the custard, it can stand on its own
Turn off the oven and I let them sit inside the oven with the door ajar for 5 minutes. This helps to minimize the egg custard from sinking too much. Remove from the oven and let them cool down for about 5 minutes then remove to the cooling rack to let them cool down further. They are best served warm or room temperature
Notes
If you don't have evaporated milk, you can use half-and-half or regular whole milk (full cream milk). I have tried both with success. I haven't tried with coconut milk though.