Use a Hand whisk to mix together half of the sugar with the egg yolk in a mixing bowl until it is slightly fluffy.
Mix in the cornstarch, flour, and vanilla until thoroughly incorporated into a smooth paste. If it is too thick, mix in a very small amount of milk.
Heat the milk with the remaining sugar until simmering. Then pour the warm milk over the egg yolk mixture slowly while whisking vigorously by hand with a Hand whisk.
Pour the mixture back into the saucepan and cook over medium heat for a few minutes until it thickens (usually 1 minute after it starts to boil).
Take the pastry cream off the heat and strain through a sieve for a lump-free end result. Then add in the soft butter in 3 stages, mixing well after each addition with a rubber spatula.
Place the cream into a shallow bowl and cover the entire surface with plastic wrap to avoid skin forming on top. Move it to the fridge to set properly for a few hours.
How to make tart crust
Sift together the flour, icing sugar, almond flour, and salt into a mixing bowl.
Add cubes of very cold butter and rub the mixture between your hands so it forms a sand-like consistency.
Slowly add the egg and mix with your hands just until the dough comes together. Then knead with the palm of your hand for a minute until it becomes smooth and form it into a disk.
If the dough is warm and sticky, place it into the fridge for 10-15 minutes first. Otherwise, roll it out to 2mm thickness between two Silicone baking mats.
Place the dough into the freezer for 15 minutes still in between the Silicone baking mats.
Take the dough out from the freezer, remove the top silicone mat, and use one of the Perforated tart rings to cut out 8 circles and form the bases of your mango tarts. Use an Offset spatula to move the circles into the rings.
Cut 8 long stripes out of the dough to make the sides of the tarts, and press each one into the sides of the rings. Place the tart shells into the freezer for one hour.
Pre-heat oven to 160℃ / 320℉
Trim the tart shells with a sharp knife and bake for 20 minutes.
Carefully remove the rings and bake for a further 5-10 minutes until golden brown. Let them cool completely on the Perforated "air" baking mat before filling.
How to assemble the mango tart
Fill the cooled tart shells up to the edge with pastry cream and smooth off the top with an offset spatula.
Cut the mango in a julienne style (thin strips) and soak up the juice using paper kitchen towels. Arrange the mango on top of the custard tarts.
Notes
Ingredient notes
Always weigh ingredients by the gram using a digital scale. Baking is about precision.
Make sure the butter for the pastry is very cold. Cut it into cubes and place it in the freezer for 15 minutes before use.
The butter for the pastry cream needs to be at room temperature/slightly softened.
Always use room-temperature eggs in baking.
Technique notes
Do not over-knead the pastry dough, and do not use a mixer.
If the pastry ever gets too warm to work with, place it in the freezer for 5 minutes and then continue.
The pastry cream mixture might get lumpy at first when you are cooking it, but just keep whisking, and the cream will get smooth and glossy.
When you come to filling the mango tarts with pastry cream, you may need to whisk it a few times after taking it from the fridge. But do not overdo it, as it can get runny. Just give it a few quick whisks until smooth.
Soak up some of the juice from the mango once you have sliced it so that the filling underneath doesn't get wet or soggy.
I like to garnish my mango tart with some gold leaf and some sprigs of herbs to give a splash of color.