BARBARA FAIRCHILD/ANDREW MCMEEL PUBLISHING
1 cup unbleached all purpose flour (for crust)
1 14-ounce can sweetened condensed milk (for caramel topping)
1⁄4 cup (packed) golden brown sugar (for crust)
1⁄2 cup (packed) golden brown sugar (for caramel topping)
2 teaspoons cornstarch (for crust)
6 tablespoons (3⁄4 stick) unsalted butter, diced (for caramel topping)
1⁄4 teaspoon salt (for crust)
2 tablespoons golden syrup (such as Lyle’s Golden Syrup) or dark (for caramel topping)
1⁄2 cup (1 stick) chilled unsalted butter, cut into 1⁄2-inch cubes (for crust)
1 teaspoon vanilla extract (for caramel topping)
1 tablespoon ice water (for crust)
6 ounces bittersweet or semisweet chocolate (do not exceed 61% cacao), chopped (for chocolate glaze)
1 large egg yolk (for crust)
3 tablespoons heavy whipping cream (for chocolate glaze)
Crust: Preheat oven to 350 degrees Fahrenheit. Butter 12x81⁄4x1-inch fluted tart pan with removable bottom. Blend flour, sugar, cornstarch, and salt in processor. Add butter. Using on/off turns, blend until coarse meal forms.
Add 1 tablespoon ice water and egg yolk. Blend until moist clumps form. Press dough onto bottom (not sides) of pan; pierce all over with fork. Bake until golden, piercing if crust is bubbling, about 22 minutes. Cool completely.
Caramel Topping: Whisk milk, sugar, butter, syrup, and vanilla in heavy medium saucepan over medium heat until sugar dissolves, butter melts, and mixture comes to boil. Attach clip-on candy thermometer to side of pan.
Boil gently until caramel is pale golden and thick and thermometer registers 225 degrees Fahrenheit, whisking constantly, about 8 minutes. Pour caramel evenly over crust, then spread almost to edge of crust; cool 15 minutes to set.
Chocolate Glaze: Meanwhile, melt chocolate with cream in microwave in 15-second intervals, stirring occasionally until smooth (do not overheat or chocolate will separate). Spread chocolate over warm caramel; sprinkle with sea salt.
Refrigerate until chocolate is set, at least 1 hour.