Combine Dry Ingredients: In a large bowl, whisk together the flour, cocoa powder, sugar, and salt.
Cut in the Butter: Add the cold, cubed butter to the dry ingredients. Using a pastry blender or your fingertips (work quickly to keep the butter cold!), cut the butter into the flour mixture until it resembles coarse crumbs.
Add the Egg Yolk: In a small bowl, lightly whisk the egg yolk. Add it to the flour mixture.
Add Ice Water: Gradually add the ice water, one tablespoon at a time, mixing after each addition. Mix until the dough just comes together. Be careful not to overmix.
Form the Dough: Gently gather the dough into a disc. Wrap it tightly in plastic wrap and refrigerate for at least 30 minutes, or up to 2 hours.
Roll Out the Dough: On a lightly floured surface, roll out the chilled dough into a circle about 12 inches in diameter.
Transfer to Tart Pans: Carefully transfer the rolled-out dough to your tart pans (4-inch individual tart pans are ideal). Gently press the dough into the bottom and up the sides of the pans.
Trim the Edges: Trim the excess dough from the edges of the tart pans.
Dock the Crusts: Use a fork to prick the bottom of the tart crusts all over.
Chill Again: Place the tart pans in the freezer for 15 minutes.
Pre-bake the Crusts: Preheat your oven to 375°F (190°C). Line the tart crusts with parchment paper and fill with pie weights or dried beans.
Bake: Bake for 15-20 minutes, or until the edges are lightly golden brown. Remove the parchment paper and pie weights and bake for another 5-10 minutes, or until the bottom of the crusts are golden brown.
Cool Completely: Let the tart crusts cool completely in the pans before filling.
Prepare the Sugar Syrup: In a medium saucepan, combine the sugar and water. Stir to moisten the sugar.
Cook the Caramel: Cook over medium heat, without stirring, until the sugar dissolves and the mixture turns a deep amber color. This will take about 8-10 minutes. Watch it carefully, as it can burn quickly.
Add the Warm Cream: Carefully pour in the warm heavy cream. The mixture will bubble vigorously, so be cautious. Whisk constantly to combine.
Add the Butter: Add the cubed butter and whisk until melted and smooth.
Remove from Heat: Remove the saucepan from the heat and stir in the vanilla extract and sea salt flakes.
Cool Slightly: Let the caramel cool slightly for about 5-10 minutes before pouring it into the tart crusts.
Fill the Tart Crusts: Pour the salted caramel filling into the cooled tart crusts, dividing it evenly among them.
Chill: Refrigerate the filled tart crusts for at least 1 hour, or until the caramel is set.
Chop the Chocolate: Finely chop the semi-sweet chocolate and place it in a heatproof bowl.
Heat the Cream: In a small saucepan, heat the heavy cream over medium heat until it just comes to a simmer. Do not boil.
Pour over Chocolate: Pour the hot cream over the chopped chocolate. Let it sit for 1 minute to allow the heat to melt the chocolate.
Whisk Until Smooth: Whisk gently until the chocolate is completely melted and the ganache is smooth and glossy.
Add Butter: Stir in the butter until melted and incorporated.
Cool Slightly: Let the ganache cool slightly for about 5-10 minutes before pouring it over the caramel-filled tart crusts.
Pour over Tarts: Pour the chocolate ganache over the chilled caramel-filled tart crusts, dividing it evenly among them.
Chill Again: Refrigerate the tarts for at least 30 minutes, or until the ganache is set.
Serve: Before serving, sprinkle the tarts with a pinch of sea salt flakes for an extra touch of flavor and visual appeal.
Storage: Store the chocolate salted caramel tarts in an airtight container in the refrigerator for up to 3 days. They are best enjoyed cold or at room temperature.
Notes
For the crust, make sure the butter is very cold. This is key to a flaky crust.
Don’t overmix the crust dough, or it will become tough.
When making the caramel, watch it carefully, as it can burn quickly. A candy thermometer is helpful.
Warm the heavy cream before adding it to the caramel to prevent it from seizing up.
Use high-quality chocolate for the ganache for the best flavor.
Maldon sea salt flakes are recommended for the caramel and garnish, but any sea salt flakes will work.