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1
Preheat oven to 325F.
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2
Line 13x9x1-inch baking sheet with parchment paper; butter parchment.
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3
Combine first 4 ingredients in medium metal bowl.
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4
Set bowl over saucepan of barely simmering water; stir until chocolate and butter melt.
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5
Remove bowl from over water; stir in salt (mixture will be grainy).
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6
Beat eggs and 2 tablespoons sugar in another medium bowl until pale, about 6 minutes; fold into chocolate mixture.
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7
Fold in flour, then hazelnuts.
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8
Spread batter evenly on baking sheet.
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9
Bake until tester inserted into center comes out with a few moist crumbs attached, about 13 minutes (cake will be thin).
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10
Transfer pan to rack.
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11
Cool cake completely.
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12
Combine chocolates in medium metal bowl.
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13
Bring 1 cup cream to simmer in small saucepan; pour cream over chocolates and let stand 1 minute.
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14
Stir until melted and smooth.
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15
Chill mixture until firm, about 2 hours.
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16
Place bowl with chilled chocolate mixture over saucepan of barely simmering water until mixture is partially melted (do not stir), about 5 minutes.
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17
Remove bowl from over water; add butter to bowl.
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18
Using electric mixer, beat until filling is thick and glossy, about 3 minutes.
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19
Using clean dry beaters, beat 1/2 cup chilled whipping cream in another medium bowl until peaks form.
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20
Fold whipped cream into filling.
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21
Cover 14x5-inch cardboard rectangle with foil.
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22
Invert cake onto work surface; remove parchment.
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23
Cut cake lengthwise in half.
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24
Place 1 cake half on foil-covered cardboard.
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25
Spread 1/2 cup chocolate filling over.
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26
Top with second cake half.
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27
Spoon remaining filling into pastry bag fitted with large plain round tip.
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28
Pipe filling atop cake in side-by-side lengthwise rows, then smooth top.
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29
Chill until filling is firm, about 1 hour.
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30
Bring cream and corn syrup to simmer in small saucepan.
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31
Remove from heat.
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32
Add chocolate; let stand 5 minutes.
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33
Stir until smooth.
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34
Add butter; stir until melted.
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35
Let stand until barely lukewarm but still pourable, about 20 minutes.
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36
Place cardboard base with cake on rack set over rimmed baking sheet.
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37
Spoon glaze over top of cake, allowing glaze to run down sides.
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38
Using offset spatula, smooth glaze over sides.
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39
Mound chocolate shards or curls over top and sides of cake.
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40
Garnish with hazelnuts and candied orange peel.
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41
Refrigerate until glaze is set, at least 2 hours.
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42
(Can be made 1 day ahead.
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43
Cover and keep chilled.)
