I use cream fraiche on the top of this tart to cut the richness and sweetness of the chocolate and caramel. Feel free to leave it off, but it is delicious. You could sprinkle with a bit of salt, as well.
Makes 1 - 9 inch tart
For the Crust:
1 cup all-purpose flour
1/4 cup unsweetened cocoa powder
1/4 cup powdered sugar
1/2 teaspoon espresso powder
1/4 teaspoon salt
1/2 cup (1 stick) cold unsalted butter, cut into cubes
1 large egg yolk
For the Caramel Filling:
1 cup granulated sugar
1/4 cup water
1/4 cup light corn syrup
6 tablespoons unsalted butter, cut into pieces
1/2 cup heavy cream
1 tablespoon strong brewed coffee it 1 teaspoon instant espresso powder dissolved in 1 tablespoon water
1/2 teaspoon vanilla extract
For the Chocolate Ganache:
6 ounces bittersweet chocolate, finely chopped
1/2 cup heavy cream
1 tablespoon unsalted butter
1/4 teaspoon espresso powder
For finishing:
¼ cup creme fraiche
2 tablespoons reserved caramel sauce
Make the crust: In a food processor, combine flour, cocoa powder, powdered sugar, espresso powder, and salt. Add the butter and pulse until the mixture resembles coarse crumbs. Add the egg yolk and pulse until the dough just comes together.
Form the dough into a disk, wrap in plastic wrap, and refrigerate for at least 1 hour.
Preheat oven to 375°F (190°C). Roll out chilled dough on a lightly floured surface. Fit into a 9-inch tart pan with a removable bottom. Trim the edges. Line with parchment paper and fill with pie weights or dried beans. Bake for 15 minutes, remove weights and parchment, bake an additional 5-7 minutes until set. Cool completely.
Make the caramel: In a medium saucepan over medium heat, combine sugar, water, and corn syrup. Cook, swirling pan occasionally (not stirring) until mixture turns amber in color. Remove from heat and carefully whisk in butter (mixture will bubble). Slowly whisk in cream and coffee. Return to medium heat and cook, whisking constantly, for 1 minute. Remove from heat and stir in vanilla and salt. Cool slightly.
Pour warm caramel (reserve 2 tablespoons to drizzle on the top of the tart) into the cooled tart shell. Refrigerate for at least 2 hours, or until caramel is set.
Make the ganache: In a heatproof bowl, combine chocolate and espresso powder. Heat the cream in a saucepan until just simmering. Pour hot cream over chocolate and let sit for 2 minutes. Whisk until smooth, then whisk in the butter. Let cool slightly.
Pour the ganache over the set caramel. Refrigerate for at least 30 minutes, or until ganache is set.
To finish:
In a circular shape, spread the creme fraiche on the top of the tart, leaving a border of 1-2 inches. Drizzle with reserved caramel.
Refrigerate until ready to serve.