In a large bowl, whisk together the flour, sugar, and salt. Add the cold cubed butter and cut it into the flour until the mixture looks like coarse crumbs. Add the ice water gradually until the dough just comes together, shape into a disk, wrap, and chill for at least 1 hour.

Preheat the oven to 375°F. Roll the chilled dough into an 11-inch circle and fit it into a 9-inch tart pan, pressing it into the edges and trimming extra dough. Line with parchment paper, fill with pie weights, and bake for 12-15 minutes. Remove weights and parchment, and bake for an additional 5 minutes until the bottom looks dry.

Lower the oven temperature to 350°F. In a large bowl, whisk together the eggs, corn syrup, dark brown sugar, melted butter, vanilla, and salt until smooth and well combined.

Scatter the pecan halves and chopped dark chocolate evenly over the bottom of the par-baked crust. Slowly pour the egg mixture over the top, filling the tart shell almost to the rim.

Bake for 38-42 minutes, until the filling is puffed and set around the edges but still has a slight jiggle in the center. Cover the crust edges with foil if they brown too quickly.

Let the tart cool completely on a wire rack for about 2 hours. Drizzle with melted dark chocolate and finish with flaky sea salt. Slice after fully cooling to ensure neat pieces.