Prepare the Crust:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease a 9-inch tart pan with a removable bottom.
2. Make the Dough: In a bowl, combine flour and powdered sugar. Cut in cold butter until the mixture resembles coarse crumbs. Add the egg yolk and ice water, mixing until the dough comes together.
3. Press into Pan: Roll out the dough and press it evenly into the tart pan. Prick the bottom with a fork to prevent bubbling.
4. Blind Bake: Line the crust with parchment paper and fill it with pie weights or dried beans. Bake for 10-12 minutes, then remove the weights and bake for an additional 3-5 minutes until golden. Let cool.

Make the Salted Caramel:

5. Melt Sugar: In a saucepan, combine sugar and water over medium heat, stirring until dissolved. Cook without stirring until it turns a golden amber color.
6. Add Cream and Butter: Remove from heat and carefully whisk in heavy cream and butter until smooth. Stir in sea salt.
7. Layer the Caramel: Pour the salted caramel over the cooled crust and spread evenly. Chill in the refrigerator for 15 minutes.

Prepare the Chocolate Ganache:

8. Heat Cream: In a small saucepan, heat heavy cream until it begins to simmer.
9. Melt Chocolate: Pour the hot cream over the chocolate chips in a heatproof bowl. Let sit for 2 minutes, then stir until smooth. Add vanilla extract.
10. Layer the Ganache: Pour the chocolate ganache over the caramel layer, spreading evenly. Chill for 1 hour until set.

Finish the Tart:

11. Add Flaky Sea Salt: Just before serving, sprinkle the tart with flaky sea salt for the finishing touch.