Salted Caramel Chocolate Tart
For the crust:
1/3 cup unsweetened cocoa powder (Dutch-process if possible)
2 tablespoons sugar
½ teaspoon Diamond Crystal kosher salt
1-2/3 cups all-purpose flour
¾ cup (1½ sticks) chilled unsalted butter, cut into tablespoon-sized pieces
1 large egg yolk
3 tablespoons chilled milk or water
For the caramel filling:
1½ cups sugar
1/8 teaspoon cream of tartar
1/3 cup water
6 tablespoons chilled unsalted butter, cut into pieces
1/3 cup heavy cream
1 teaspoon Diamond Crystal kosher salt
For the ganache:
4 ounces semisweet chocolate (do not go above 70% cacao), finely chopped
4 ounces (½ cup) heavy cream
2 tablespoons unsalted butter, cut into small pieces
Flaky sea salt or Fleur de Sel
A 9-or 10-inch tart pan with removable bottom
For the crust: Whisk cocoa, sugar, salt and 1-2/3 cups flour in a medium bowl. Add butter and toss to coat. Using your fingers, smash butter into dry ingredients until it nearly disappears (you shouldn't see any large bits) and mixture holds together when squeezed -- work it more than you would pie dough. Make a well in the center and add yolk and milk. Using a fork, gradually incorporate the flour mixture until you've got a shaggy dough. Knead a couple of times in the bowl until no dry spots remain and the dough is smooth. Flatten into a ¾-inch thick disk, wrap tightly in plastic wrap and chill until firm, about 2 hours. (You may also use a food processor to make the crust using a typical pie crust method.)
Preheat oven to 350 degrees. Let dough sit 5 minutes to soften slightly. Roll out between two sheets of parchment paper, or plastic wrap, to about 14-inches round and about 1/8-inch thick. (I find this keeps adding additional flour to a minimum.) Once desired diameter is achieved, remove top layer of parchment and invert dough on top of tart pan. Gently remove parchment and press dough firmly into bottom of pan with floured hands, then use a straight-sided measuring cup to firmly press sides of dough into grooves and up sides of pan. Use a rolling pin over top edge of pan to shear off excess dough, reserving dough scraps for patching any potential cracks later. Prick bottom of dough all over with a fork and chill in freezer until very firm, 10 to 15 minutes.
Place tart pan on a rimmed baking sheet and line with a sheet of parchment paper or foil. Fill with pie weights or dried beans and bake until edges of crust are set and starting to look dry, 12 to 15 minutes. Carefully lift out parchment with weights and patch any visible cracks with reserved dough. Return crust to oven and bake until firm and dry all over, 18 to 22 minutes. Transfer to a wire rack and let cool.
Caramel filling: Bring sugar, cream of tartar and 1/3 cup water to a boil in a large saucepan over medium-low, stirring with a heatproof spatula until dissolved. Cook, swirling pot often but not stirring, until mixture turns deep amber, 8 to 10 minutes. Remove caramel from heat and immediately stir in butter a piece at a time until smooth (be careful; mixture will sputter). Gradually stir in cream, then add salt. Transfer caramel to a heatproof measuring cup. Let cool until warm.
Pour caramel into cooled tart shell. Chill until caramel is set, at least 1 hour.
Ganache: Place chocolate in a heatproof bowl. Heat cream and butter in a saucepan over medium heat to a gentle simmer, but not boiling. Pour over chocolate and allow to sit 5 minutes; stir with whisk until mixture is smooth. Allow mixture to cool until slightly thickened.
Pour over caramel layer, smoothing to the edges with offset spatula or back of spoon. Sprinkle with sea salt flakes and allow to set until ganache has lost its sheen, about 15 minutes.
Best if served at room temperature. Store in a cool place if not eaten right away.
Tasks you can do ahead: Dough can be made two days ahead; keep chilled. Crust can be baked one day ahead. Store tightly wrapped at room temperature.
Caramel filling can be made three days ahead; cover and chill. Microwave in 20-second intervals, stirring in between, just until pourable. Caramel-filled tart can be made one day ahead; once it's set, cover and keep chilled.
Tart can be assembled one day ahead. Chill until ganache is set, then cover loosely. Let sit at room temperature 15 minutes before slicing.
Penny Kazmier, adapted from a recipe in Bon Appétit at bonappetit.com/recipe/salted-caramel-chocolate-tart