Ingredients

  • 1/2 cup hazelnuts, toasted and any loose skins rubbed off in a kitchen towel, then cooled completely
  • 1 cup all-purpose flour
  • 3 tablespoons sugar
  • 1/2 teaspoon salt
  • 1/2 stick (1/4 cup) cold unsalted butter, cut into pieces
  • 1 large egg
  • 1 teaspoon vanilla
  • 7 ounces semisweet chocolate, finely chopped
  • 1/2 cup whole milk
  • 1/4 cup sugar
  • 1/4 teaspoon salt
  • 2 large egg yolks
  • 1 teaspoon vanilla
  • 1 cup creme fraiche
  • Special equipment: a 9- by 1-inch fluted round tart pan with removable bottom; pie weights or raw rice

Method

  • Preheat oven to 350F.
  • Pulse hazelnuts with flour, sugar, and salt in a food processor until finely ground (be careful not to grind to a paste), then add butter and pulse until most of mixture resembles coarse meal with some roughly pea-size butter lumps.
  • Add egg and vanilla and pulse just until mixture begins to clump.
  • Press dough evenly over bottom and up side of tart pan and chill 10 minutes.
  • Line tart shell with foil and fill with pie weights.
  • Bake in middle of oven until pale golden along rim, about 15 minutes.
  • Carefully remove foil and weights and bake shell until bottom and side are golden, about 10 minutes more.
  • Cool in pan on a rack 10 minutes.
  • Reduce oven temperature to 325F.
  • Put chopped chocolate in a bowl.
  • Bring milk, sugar, and salt to a boil in a 1-quart saucepan over moderate heat, stirring, then pour milk over chocolate in bowl and let stand until chocolate is melted, about 1 minute.
  • Whisk until smooth, then whisk in yolks and vanilla.
  • Whisk in creme fraiche and pour into crust.
  • Bake tart in middle of oven until just set, 20 to 25 minutes.
  • Cool completely in pan on rack.
  • Chill until firm, at least 1 hour, then bring to room temperature before serving.