-
1
Preheat oven to 350F.
-
2
Butter 10-inch-diameter springform pan; line bottom with parchment paper round.
-
3
Stir chocolate in metal bowl set over saucepan of simmering water until melted and smooth.
-
4
Cool slightly.
-
5
Using electric mixer, beat sugar and butter in large bowl 2 minutes.
-
6
Beat in egg yolks, Grand Marnier, orange peel, and vanilla.
-
7
Stir in lukewarm chocolate.
-
8
Add flour and salt; stir to blend.
-
9
Using clean dry beaters, beat egg whites in another large bowl until peaks form.
-
10
Fold whites into chocolate mixture in 3 additions.
-
11
Transfer batter to prepared springform pan.
-
12
Bake cake until top is dry and cracked and tester inserted into center comes out with a few moist crumbs attached, about 45 minutes.
-
13
Cool cake in pan on rack (top will fall slightly).
-
14
DO AHEAD: Can be made 1 day ahead.
-
15
Cool completely; cover and let stand at room temperature.
-
16
Place chocolate and butter in medium metal bowl.
-
17
Bring cream to boil in small saucepan.
-
18
Pour hot cream over chocolate mixture; stir until mixture is melted and smooth.
-
19
Run thin knife around inside of cake pan; remove pan sides.
-
20
Invert cake onto 10-inch removable tart pan bottom or cardboard round.
-
21
Place on rack set in rimmed baking sheet.
-
22
Remove cake pan bottom and parchment.
-
23
Pour icing over cake and spread to cover top and sides (any icing that drips onto baking sheet can be reused).
-
24
Chill until glaze sets, about 30 minutes.
-
25
DO AHEAD: Can be made 1 day ahead.
-
26
Cover with cake dome and chill.
-
27
Let stand at room temperature 1 hour before serving.
-
28
Cut into wedges and serve.
