In a food processor, combine flour and powdered sugar. Add cold butter and pulse until the mixture resembles coarse crumbs.

Add egg yolk and ice water one tablespoon at a time until the dough begins to hold together. Form into a disk, wrap in plastic wrap, and refrigerate for at least 30 minutes.

Preheat your oven to 375°F (190°C). Roll out the chilled dough on a floured surface and fit it into tart pans. Prick the base with a fork to prevent bubbling.

Bake for about 15-20 minutes, or until lightly golden. Allow to cool completely.

Heat heavy cream and granulated sugar in a saucepan over medium heat until just simmering. Pour it over the chopped dark chocolate in a bowl and let it sit for a few minutes. Stir until smooth, then mix in vanilla extract.

Pour the chocolate filling into the cooled tart shells and refrigerate until set, about 2 hours.

In a saucepan over medium heat, cook granulated sugar until it melts into an amber-colored liquid, stirring occasionally. Carefully add butter and heavy cream; stir until smooth. Remove from heat, add sea salt, and let cool slightly.

Top the chilled chocolate tarts with warm salted caramel, allowing it to spill over the edges. Chill in the refrigerator for about 30 minutes for the flavors to meld.

Garnish with additional sea salt and maybe some whipped cream, if desired. Serve cold or at room temperature, and enjoy!