In a large mixing bowl, beat the butter and sugar together until fluffy. Add the egg yolks and vanilla and beat to combine.
Add the flour into the bowl along with the salt. Mix until the dough just comes together. Shape the dough into a disc, wrap in plastic wrap, and chill in the refrigerator for 1 hour.
Lightly dust your work surface with flour. Remove the dough from the plastic wrap and begin to roll it into a round that is approximately 11-inches (28 cm) wide and ½-centimetre thick (to fit in a 9-inch non-stick tart pan with a removable bottom). Make sure to flour your rolling pin and periodically rotate the dough so that it does not stick to your work surface. Gently press the dough into the tart pan without stretching it and trim the edges. Place the tart in the refrigerator for 20 minutes to chill before baking.
Preheat the oven to 350°F.
When you are ready to bake the tart, remove the tart shell from the fridge. Pierce the bottom of the tart shell several times with the tines of a fork to prevent the tart from rising. Place in the oven and bake for 18-20 minutes, or until golden brown.
Remove the tart shell from the oven and let cool completely.
While the tart shell is cooling, make the custard. Place 1 cup of milk into a small pot over medium heat. Bring the milk to just below a simmer.
In a separate bowl, add the sugar, eggs, and cornstarch. Mix to combine. Add ¼ of the warm milk to the egg mixture and mix to combine. Then add the egg mixture to the pot of milk. Whisk constantly over medium heat until the custard has thickened, about 5 minutes.
Remove from the heat and add the vanilla and butter. Transfer to a bowl and let cool completely.
To assemble to tart, fill the cooled sweet tart crust with the vanilla custard. Use an offset spatula to spread the custard into an even layer. Place in the refrigerator to set for 30 minutes. Arrange the sliced strawberries in concentric circles and serve immediately. Enjoy!