In a food processor, add flour and salt. Pulse a few times to combine.
Add the butter and shortening and pulse until the mixture becomes crumbly.
Add the egg yolk and mix to combine.
While the processor is running, stream the water through the feed chute and mix until incorporated.
Remove the dough from the processor and form it into a disc.
Cover the dough with plastic wrap and place it in the fridge to chill for 30 minutes.
PREHEAT OVEN AND PREP PANS:
Move the oven rack to the middle position and preheat the oven to 425°F.
Lightly spray 4, 4-inch tart pans with non-stick baking spray.
FORM, BAKE, AND COOL THE CRUST:
Divide the chilled dough evenly between the four pans and press into the bottom and sides of each pan.
Cut off any excess from the top of each pan. Cover each pie crust with parchment paper and place pie weights or lentils on top.
Place the pans into the preheated oven and bake for 24 minutes.
Once baked, remove from the oven and place on a wire cooling rack to cool completely. While the crust is baking, prepare the filling.
MAKE THE FILLING:
Whisk together milk and vanilla bean paste in a medium saucepan over medium heat.
Once the milk begins to simmer, remove it from the heat.
Whisk together sugar, cornstarch, salt, and egg yolks in a separate mixing bowl until smooth and pale.
Slowly pour the hot vanilla milk into the bowl while whisking to temper the eggs.
Once all the milk is incorporated, pour the mixture back into the pan.
Return the pan to the heat.
Continue whisking until the mixture begins to bubble. Once bubbling, let cook for exactly 1 minute, then remove from the heat.
Add the butter and mix until the butter is melted and incorporated.
Transfer the mixture to a bowl and let cool for 30 minutes.
ASSEMBLE:
Spoon the cooled filling into the tartlets and place them into the fridge to chill for 3 hours.
Once the tartlets have chilled, make the glaze. In a microwave-safe bowl, combine strawberry jelly and water and heat in the microwave for 20-30 seconds.
Once heated, remove from the microwave and mix until smooth.