Chocolate Tart Dough:
1/2 cup unsalted butter (1 stick), at room temperature
1/2 cup plus 1 tablespoon confectioners' sugar
1/4 cup unsweetened cocoa
1 large egg yolk
3/4 teaspoon vanilla extract
1 1/4 cups all-purpose flour
1/2 cup water
2 cups sugar
1/4 cup light corn syrup
1/2 cup (1 stick) unsalted butter
1/2 cup heavy cream
2 tablespoons creme fraiche
1/2 cup heavy cream
3 1/2 ounces extra-bittersweet chocolate, chopped
A pinch fine sea salt, such as fleur de sel
To prepare the tart dough, in the bowl of an electric mixer fitted
with the paddle attachment, cream the butter and confectioners'
sugar until combined, about 1 minute. Add the cocoa and beat until
incorporated. Add the egg yolk and vanilla and beat until smooth.
Sift in the flour and beat on low speed until just combined. Scrape
the dough onto a sheet of plastic wrap and form it into a disk. Wrap
and chill until firm, about 1 hour, or up to 3 days.
Preheat oven to 325 degrees F.
On a lightly floured surface, roll the tart dough 3/16-inch thick.
Using a 2 1/2-inch round cutter, cut out 24 rounds of dough and
press them into mini-muffin tins or 2 dozen 2-inch tart pans,
trimming away any excess dough; prick the dough all over with a
fork. Chill the tart shells for 20 minutes.
Line the tart shells with foil and fill with dried beans, rice, or
pie weights. Bake for 15 minutes. Remove foil and weights and bake
for 5 to 10 minutes longer or until the pastry looks dry and set.
Transfer to a wire rack to cool. Remove cooled shells from tart pans
and transfer to a plate.
To prepare the filling, place the water in a large saucepan. Add the
sugar and corn syrup and cook the mixture over medium-high heat,
swirling the pan occasionally, until you have a dark amber caramel,
about 10 minutes. Carefully whisk in the butter, cream, and creme
fraiche (the mixture will hiss and bubble up so stand back),
whisking until smooth. (The caramel can be made up to 5 days ahead
and refrigerated). Divide the caramel among the tart shells while
still warm (or reheat the caramel in the microwave or over low heat
until it is pourable) and let sit until the caramel is set, at least
To make the glaze, in a saucepan, bring the cream to a boil. Place
the chocolate in a bowl. Pour the hot cream over the chocolate, add
a pinch of sea salt, and let sit for 2 minutes, then whisk until
smooth. Pour some of the glaze over each of the tarts while it is
still warm. Let the glaze set at room temperature for at least 2
hours before serving.