In a mixing bowl, combine the all-purpose flour, powdered sugar, and salt, stirring until well blended. Add the cold cubed butter and use a pastry cutter or your fingers to mix until the mixture resembles coarse crumbs. Incorporate the egg yolk and gradually add 2-3 tablespoons of ice water, mixing until the dough holds together but is not sticky. Transfer the dough into a tart pan, pressing it evenly into the bottom and up the sides. Use a fork to prick the bottom to prevent bubbling.
Preheat your oven to 350°F (175°C). Place the prepared crust in the oven and bake for 15-20 minutes, or until it turns a light golden color. Once done, remove the crust from the oven and allow it to cool completely in the tart pan.
In a medium saucepan over medium heat, add the granulated sugar. Allow the sugar to melt, stirring occasionally, until it achieves a deep amber color (about 8-10 minutes). Be careful not to burn it! Once melted, carefully whisk in the cubed butter until it is fully incorporated and the mixture is smooth. Gradually add the heavy cream while whisking continuously to combine. Remove from heat and stir in the sea salt and vanilla extract. Allow the caramel to cool slightly before using.
Pour the cooled salted caramel into the baked tart crust, using a spatula to spread it evenly. Place the tart in the refrigerator for about 30 minutes to allow the caramel to set.
In a clean saucepan, heat the heavy cream over medium heat just until it begins to simmer (do not boil). Remove from heat and pour the hot cream over the chocolate chips in a mixing bowl. Allow it to sit for 2 minutes, then stir until the chocolate is melted and the mixture is smooth. Finally, mix in the unsalted butter until the ganache is shiny and velvety.
Gently pour the chocolate ganache over the chilled salted caramel layer, smoothing it out with an offset spatula to create a nice surface. Return the tart to the refrigerator for an additional hour, or until the ganache is set.
Once the tart is set, remove it from the refrigerator and slice it into wedges. For an extra touch, sprinkle a few flakes of sea salt on top before serving to enhance the flavors.
Notes
Serve with a sprig of mint or a dusting of cocoa powder for garnish.