7ouncesall-purpose flour(198g or 1 1/4 cup + 2 tablespoons)
2ouncescornstarch(58g or 1/4 cup + 2 tablespoons)
1 1/2teaspoonskosher salt
1 1/2teaspoonsbaking powder
1/2cupwhole milk
1/2cupheavy cream
1 1/2tablespoonspure vanilla extract
6ouncesunsalted butter,cubed and at room temperature
12ouncesgranulated sugar(341g or 1 3/4 cup)
4largeeggs
For the Buttercream
13ouncesgranulated sugar(1 1/2 cups)
1/4 cup+ 2 tablespoons water
Optional: 1 teaspoon corn syrup
5 largeegg whites
16 ounces unsalted butter, cubed and at room temperature (preferably left out overnight)
1 1/2teaspoonspure vanilla extract
4ouncesunsweetened chocolate,melted
Instructions
Prepare the cake
Place a rack in the center of the oven and preheat to 350 degrees F. Lightly grease the bottom of two 8 or 9-inch cake pans (avoid the sides) and top with parchment rounds. Place the pans on a baking sheet (this will make it easy to take both cakes in and out of the oven at once).
In a medium bowl, whisk together the flour, cornstarch, salt, and baking powder. In a liquid measuring cup, combine the milk, cream and vanilla. Crack the eggs into a bowl or liquid measuring cup.
In a stand mixer fitted with the paddle attachment, combine the butter and sugar on low for 2-3 minutes, then turn up to medium speed and cream for 1-3 minutes, until pale and fluffy.
Turn the speed down to low and slowly add the eggs, one at a time, stopping to scrape down the bowl all the way to the bottom after the second and last egg. Wait until each egg is incorporated before adding the next one. The batter may look slightly broken by the end of this step.
On medium speed, alternate between adding the dry and wet ingredients, beginning and ending with the dry ingredients. This shouldn’t take longer than a minute.
Thoroughly scrape down the bowl all the way to the bottom to make sure there are no hidden dry patches, then turn the speed up to medium and mix for an additional 10-15 seconds.
Spread the batter evenly into the prepared cake pans. Use a spatula to even out the tops (don’t skip this step).
Bake for 28-30 minutes, until a toothpick comes out clean from the center. Cool to room temperature before removing from the pan. Use an offset spatula or small knife to help detach the sides of the cake from the pan, then place a cardboard round or large cutting board against the cake pan and gently flip.
Prepare the Buttercream
Add sugar, water and corn syrup (if using) to a medium-sized sauce pot. Cover and turn the heat to high. Once the liquid begins to simmer and steam has developed, remove the cover. Using a digital thermometer, cook the sugar to the soft boil stage, 235-240 degrees F.
While the sugar syrup is cooking, whisk the egg whites on high in a stand mixer with the whisk attachment until a soft peak has formed.
Turn the speed down to medium-low and slowly pour the syrup down the side of the bowl into the eggs. Try not to pour the hot syrup directly into the meringue.
Once the syrup is completely incorporated, turn the speed to high and let the meringue form a stiff peak while cooling to room temperature, approximately 20 minutes.
Once the meringue is room temperature, begin slowly incorporating the butter on medium speed. Once all of the butter has been incorporated, turn the mixer speed up to high and slowly add the vanilla and melted chocolate.
Assemble the Cake
Place a first layer of cake on a revolving cake stand and remove the parchment paper. Placing a cardboard round below the cake is optional but strongly recommended; it will make transporting the cake much easier after it is assembled.
Spread approximately one cup of buttercream on the cake and spread it around evenly with an offset spatula. Add more buttercream as needed to reached the desired thickness. Repeat with the second layer (don't forget to remove the parchment.
Use an offset spatula to apply a thin layer of frosting to the side and top of the cake. Chill in the refrigerator for 30 minutes to set this first layer of buttercream. Cover the entire cake with a final layer of frosting. Grate some unsweetened or semi-sweet chocolate on top of the cake for decoration, if desired.
Cake is best when served at room temperature. It can be stored for 3-4 days on the counter using a covered cake stand, a large, inverted bowl, or by covering loosely with aluminum foil or plastic wrap. Make sure the cake is at room temperature before covering to avoid trapping moisture. Enjoy within a few days for best flavor and texture.