- Crust: Whisk the flour, cocoa, salt and baking soda together in a medium bowl. Put the butter, confectioners’ and brown sugar in a food processor and process until smooth and creamy. Add the dry ingredients and pulse to combine. Add the egg yolks and continue to pulse to make a smooth dough. Remove the blade, and turn dough out onto a large sheet of plastic wrap, form into a disk, and wrap tightly. Refrigerate at least 1 hour or up to 2 days.
- Meanwhile, make the filling: Put the chocolate in a medium bowl. Put the cream and sweetened condensed milk in a small saucepan and bring to a simmer over medium heat. (Alternatively, heat the cream and milk in the microwave.) Pour the cream over the chocolate and whisk until smooth and shiny. Whisk in the eggs and vanilla until smooth. Cover, and set aside at room temperature.
- Place the dough between 2 pieces of parchment paper or waxed paper and roll out into a circle about 1/4-inch thick. Refrigerate for 15 minutes.
- Position a rack in the middle of the oven and preheat to 400 degrees F. Peel off the top piece of parchment from the dough, then gently flip dough into tart pan, peeling away the rest of parchment. Carefully press dough into the tart pan so that it sits evenly in the pan. Trim excess dough from the edges, if needed. Line the crust with waxed paper or lightly sprayed parchment paper and fill with pie weights or baking beans.
- Place the tart shell on a baking sheet and bake for 20 minutes. Remove the paper and weights and continue to bake until the crust sets and looks a little dull (a sign it is cooked), about 5 minutes more. Reduce oven temperature to 325 degrees F.
- Remove tart pan from oven and spread the dulce de leche evenly over the warm crust. Then top with the chocolate filling. Bake until the filling sets around edges but is still slightly wobbly in the center, about 25 to 30 minutes. Cool completely.
- Serve. For a final flourish, sprinkle lightly with gray salt just before serving, if desired.Busy Bakers’ Tips:
– Make dough and freeze for up to a month ahead.
– Form, bake and freeze crust, tightly wrapped, for up to 1 week.
– Assemble and refrigerate up to 2 days, tightly wrapped.