-
1
Preheat oven to 350F.
-
2
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.
-
3
Add egg and vanilla and pulse just until mixture begins to clump.
-
4
Press dough evenly over bottom and up side of tart pan and chill 10 minutes.
-
5
Line tart shell with foil and fill with pie weights.
-
6
Bake in middle of oven until pale golden along rim, about 15 minutes.
-
7
Carefully remove foil and weights and bake shell until bottom and side are golden, about 10 minutes more.
-
8
Cool in pan on a rack 10 minutes.
-
9
Reduce oven temperature to 325F.
-
10
Put chopped chocolate in a bowl.
-
11
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.
-
12
Whisk until smooth, then whisk in yolks and vanilla.
-
13
Whisk in creme fraiche and pour into crust.
-
14
Bake tart in middle of oven until just set, 20 to 25 minutes.
-
15
Cool completely in pan on rack.
-
16
Chill until firm, at least 1 hour, then bring to room temperature before serving.
