-
1
Heat the oven to 350 degrees F and arrange a rack in the middle.
-
2
Coat an (8-inch) cake pan generously with butter, then flour, tapping out any excess flour; set aside.
-
3
Whisk flour, baking powder, and salt in a medium bowl to combine; set aside.
-
4
In the bowl of a stand mixer fitted with a whisk attachment, combine oil, water, vanilla, egg yolks, and 1/2 cup plus 2 tablespoons of the sugar.
-
5
Whisk on medium speed until mixture is light in color and looks slightly thickened, about 5 minutes.
-
6
Turn off the mixer and, using a rubber spatula, scrape down the sides of the bowl.
-
7
Add reserved dry ingredients, turn the mixer to low, and whisk until smooth, about 1 minute.
-
8
Transfer batter to a large bowl.
-
9
Wash and dry the mixer bowl and whisk attachment.
-
10
Place egg whites in the bowl and whisk on high speed until soft peaks form (they should droop over like soft-serve ice cream), about 30 seconds.
-
11
Gradually add the remaining 2 tablespoons sugar and continue whisking until stiff peaks form (they should stand straight up), about 1 minute more.
-
12
Using a rubber spatula, fold a quarter of the egg whites into the batter until evenly incorporated; gently fold in the remaining egg whites until just combined and no large white streaks remain.
-
13
Pour the batter into the prepared pan.
-
14
Bake until the surface of the cake is golden brown and springs back when pressed and a toothpick or cake tester inserted into the center comes out clean, about 25 to 30 minutes.
-
15
Place on a wire rack to cool slightly, about 15 minutes.
-
16
Carefully run a knife around the perimeter and turn the cake onto the rack to cool completely.
-
17
Place chocolate in a medium heatproof bowl; set aside.
-
18
Place cream in a small saucepan over medium heat and bring to a simmer.
-
19
Pour over chocolate and let stand until chocolate has softened, about 5 minutes.
-
20
Add butter and stir until smooth.
-
21
Let cool slightly before using.
-
22
Place ice cream in the refrigerator until slightly softened, about 30 minutes.
-
23
Place the cooled cake in the refrigerator to chill, about 30 minutes.
-
24
(Chilling the cake ahead of time will prevent the ganache from streaking.)
-
25
Meanwhile, cut a 30-inch-long piece of parchment or waxed paper and fold it lengthwise until it is 4 inches wide.
-
26
Place a small saucepan of water over low heat and bring to a simmer.
-
27
Once the cake is chilled, slice it horizontally into 2 equal disks.
-
28
Place the top half of the cake cut side up on a large, flat dish or baking sheet.
-
29
Return the second half to the refrigerator.
-
30
Tightly wrap the parchment strip around the perimeter of the cake so that it is flush with the dish or baking sheet, to make a collar.
-
31
Tape to secure.
-
32
(The collar will keep the ganache and ice cream from running over the side of the cake.)
-
33
Measure 1 1/4 cups of the warm ganache and pour it over the parchment-wrapped cake, tilting the dish or baking sheet until the ganache reaches the parchment collar and evenly coats the top.
-
34
Place the cake on a flat, even surface of the freezer until the ganache has set, about 15 minutes.
-
35
Place the bowl of remaining ganache over the saucepan of simmering water; remove the saucepan from heat.
-
36
Remove the softened ice cream from its container and transfer to a large bowl.
-
37
Stir with a rubber spatula or wooden spoon until it is spreadable but not liquidy.
-
38
Working quickly, spread the softened ice cream over the ganache (leaving any melted ice cream in the bowl), smoothing it into an even layer until it reaches the parchment collar.
-
39
Remove the bottom cake half from the refrigerator and fit it cut side down inside the parchment collar and on top of the ice cream, then press lightly.
-
40
Remove the bowl of ganache from the saucepan, dry any condensation that has formed on the bottom of the bowl, and stir until smooth.
-
41
Pour the remaining ganache over the top of the cake and tilt the dish or baking sheet to evenly coat.
-
42
Immediately place the cake in the freezer until the ice cream is firm, at least 3 hours.
-
43
When ready to serve, remove the cake from the freezer, remove the parchment collar, and let the cake sit for 15 to 20 minutes before slicing.
-
44
If not serving immediately, remove it from the freezer once completely frozen, remove the parchment collar, wrap the cake entirely in plastic wrap, and store in the freezer for up to 1 week.
