Preheat oven to 350°F (175°C).
In a bowl, mix flour, powdered sugar, and salt.
Add softened butter and egg yolk; mix until crumbly.
Press the mixture into a tart pan evenly.
Bake for 15 minutes until golden, then cool.
In a saucepan, heat heavy cream until simmering.
Remove from heat and add chopped chocolate; stir until smooth.
In a bowl, whisk eggs and granulated sugar until combined.
Add chocolate mixture and vanilla; mix well.
Pour filling into the cooled crust and bake for 10 minutes.