Double Chocolate Tart Recipe

In bowl of food processor, pulse flour, confectioners' sugar, cocoa, and salt until combined, about 3 one-second pulses. Add butter and pulse until mixture is consistency of wet sand, with no visible bits of butter remaining, about 10 to 15 quick pulses. Add yolk and pulse until dough just begins to come together. Wrap dough with plastic wrap into 5-inch disc and chill until firm, about 30 minutes.
While the dough is chilling, make the filling. Place chocolate, sugar, and espresso powder in medium bowl. In small saucepan, heat milk and cream until simmering. Pour over chocolate and let sit 5 minutes. Whisk until smooth. Whisk in egg and vanilla; set aside.
Adjust oven rack to middle position and preheat oven to 350u0b0F. Roll out dough between 2 pieces of parchment paper, plastic wrap, or on lightly floured surface to 13-inch circle. Gently roll up dough with rolling pin and roll out over tart pan. Press dough into bottom and sides of tart pan. Chill in freezer for 15 minutes. Gently line inside of tart with foil and fill with pie weights. Bake until crust is set, about 25 minutes. Carefully remove foil with pie weights and briefly cool on wire rack 10 minutes.
Pour filling into crust and bake until edges are set and middle is slightly jiggly, 15 to 20 minutes. Let cool on wire rack at least 45 minutes before serving.