Make the Creme Patissiere ahead of time. It needs to be at least two hours ahead, but I like to make it the day before and let it rest overnight.
Make the Tart Cases
Cut butter into small chunks, then add to a bowl with the flour.
Rub the butter into the flour until all the large lumps are gone and the mixture resembles bread crumbs.
Mix in the sugar.
Lightly beat the egg in a separate bowl, then mix it into the pastry with a fork.
Add milk as necessary, 1 tablespoon at a time until the pastry comes together into a dough. You may not need to use all the milk.
Wrap the dough in plastic wrap or a ziplock bag and place in the fridge to chill for at least 30 minutes before rolling out.
Once chilled, roll the dough out gently to about 3mm thickness.
Cut out circles slightly bigger than your tart cases and press the pastry into the cases, push the pastry right to the edge of the cases and trim the top, place back in the fridge to chill for 20 minutes while you preheat your oven to 375°F / 190°C (180° in fan-assisted oven).
Blind bake the tart cases by filling with baking paper and baking beans or uncooked rice. Bake for 6 minutes and then remove the beans/rice and baking paper and bake for a further 6-7 minutes. Remove from the oven and cool completely before filling.
Take two tablespoons of the sugar and put into a bowl along with the egg yolks, flour and cornstarch - whisk to combine.
Put the remaining sugar into a saucepan with the milk and vanilla, and slowly warm over a medium-low heat.
When it begins to get warm, drizzle a small amount of warm milk into the egg yolk mixture and whisk, then add a little more, repeat until everything is together in the bowl, then pour the whole mixture back into the saucepan. It's important to do this slowly and gradually so you don't scramble the eggs
Keep heating the mixture, whisking constantly until it begins to boil. Boil for one minute or until you see thick bubbles bursting on the surface. It should be thick enough that you can draw a line in it on the back of a spoon - if it isn't, keep boiling until you reach that stage. Remove from the heat.
Pass the pastry cream through a sieve into a bowl to make sure there are no lumps.
Whisk in the butter one small piece at a time, making sure it melts into the mixture completely before adding the next piece.
Cover with plastic wrap (make sure the plastic wrap is touching the surface of the pastry cream to prevent a skin from forming) and refrigerate for at least two hours. I like to make this the day before and let it sit overnight, but it can be used after 2 hours.
Make the Strawberry Glaze
Put all the glaze ingredients into a saucepan over a medium heat.
Stirring constantly, heat until the strawberries start to break down and the mixture begins to thicken. Use a potato masher to break down the strawberries completely.
Bring the strawberry glaze to a boil and reduce until thick bubbles are popping.
Remove from the heat and pass through a sieve to remove the strawberry seeds and lumps.
Let cool completely before using.
Assemble the Strawberry Tarts
Assemble these tarts right before serving, as they will go slightly soggy if left to sit for too long.
Fill the tart cases evenly with pastry cream.
Top with fresh strawberries in whatever way you want - sliced/whole/piled up/in a pattern, whatever tickles your fancy. Try to look for the prettiest strawberries, but don't worry too much as the glaze will cover up most of the imperfections.
Generously brush the cooled strawberry glaze over the strawberries.
Enjoy! These are best eaten right away or at least on the same day.
Notes
If you don't want to make the tart cases from scratch, you can buy ready-made tart cases or buy a ready-made pastry and bake them at home. Note: The tarts are best assembled shortly before serving, as the custard can make the pastry go a little soggy if left to sit for a long time. You can make all the elements ahead of time and assemble when you are ready to serve.