This Chocolate Champagne Cake has super chocolatey champagne cake with champagne Italian meringue buttercream and dark chocolate ganache! For your next celebration, or anytime!
Preheat oven to 350° F. Grease two 8-inch cake pans (see note) and set aside.
In a medium bowl, combine dry ingredients (flour, sugar, cocoa powder, baking soda, baking powder, and salt). Set aside.
In a large bowl, combine eggs, buttermilk (see note), oil, vanilla extract, and chocolate extract (see note). Mix to combine.
Add the dry ingredients gradually, mixing until just combined.
Add champagne and coffee (see note). Mix until smooth.
Divide the batter among the prepared pans (see note on weighing batter).
Bake 20-25 minutes, or until the tops of the cakes are set and no longer wiggle. Allow cakes to cool completely on a wire rack.
For Buttercream:
Pour champagne into a small saucepan. Over medium-high heat, reduce champagne to about 2 tablespoons in volume, about 5-7 minutes. Reduction will be syrupy. Allow to cool completely.
Put egg whites into the bowl of a stand mixer. Set aside.
In a small saucepan, combine water and ½ cup sugar. Stir to moisten sugar, but do not stir after that. Stirring the sugar syrup promotes crystallization of the sugar, when that's the opposite of what you want.
Warm over low heat until sugar dissolves. Once sugar is dissolved, increase heat to medium-high. Cook until syrup reaches 246-250° F. (See notes for helpful tips on how to do this without a thermometer.)
When syrup reaches 240° F, begin beating the egg whites using the whisk attachment. Once frothy, add cream of tartar and remaining ¼ cup sugar. Beat on high until stiff peaks form.The goal is for the egg whites to reach stiff peaks at the same time the syrup reaches temperature. If the egg whites are done early, let the mixer run on low speed until the syrup comes to temperature.
Once syrup is to temperature, remove from the heat. With the mixer running on low speed, carefully pour the syrup into the egg whites in a slow, steady stream. Don't worry about scraping out the saucepan to get every last bit of syrup. Keep your focus on not burning yourself. Be VERY careful not to touch the syrup, as it will stick to your skin and can cause serious burns!
Beat mixture on medium-high until the bottom of the bowl is no longer warm to the touch, about 10 minutes. Then add butter, 2-3 tablespoons at a time, allowing the butter to incorporate completely after each addition before adding the next.
With mixer on low, drizzle in champagne reduction. Beat to combine. Frost cooled cake layers with the buttercream. Reserve some buttercream to pipe on top of the cake, if desired. Chill frosted cake to prepare for the ganache.
For Ganache:
Combine chocolate and cream in a medium heatproof bowl. Microwave on 15-second intervals, stirring after each interval, until ganache is smooth. Let cool slightly to let the ganache thicken a bit.
While still warm and pourable, pour over the top of the cake, spreading the ganache with an offset spatula and allowing the ganache to drip down the sides, if desired.
After ganache has set, pipe reserved buttercream on top of ganache, if desired. Store covered cake on your kitchen counter.Enjoy!
Notes
Note on buttermilk: If you don't have buttermilk, you can make a quick substitution with milk (2% milkfat or greater) and white vinegar or lemon juice. For this recipe, pour 1 tablespoon lemon juice or white vinegar into a liquid measure, then add enough milk to come up to the 1 cup line. Let sit for 5 minutes, then it's ready for use!Note on chocolate extract: Chocolate extract lends an amazing depth of flavor to chocolate baked goods! If you can't find it in your local grocery store, you can find some here. Even better, makes yourself some Homemade Chocolate Extract for next time!Note on coffee: The cake won't taste like coffee, I swear! The coffee enhances the chocolate flavor, and I highly recommend it! If you would prefer not to use coffee, you can use hot water instead.Note on cake pans: This recipe is for a two-layer 8" cake. I suggest using 8" pans with tall (3") sides since the cakes are quite tall.Note on weighing batter: To ensure I have the same amount of batter in each pan, I use my kitchen scaleand weigh the pans/batter.Regarding the appropriate temperature for syrup for buttercream: The best way to ensure that you've brought the syrup to the appropriate temperature is to use a candy thermometer. That said, there are a few things that you can do to make this buttercream without one: First, the bubbles across the top of the syrup will cover the top of the syrup when it's just about to temperature. Secondly, you can check to see if your syrup has reached the "soft ball" stage. To do this, simply drip a drop of the syrup into some ice water. If the syrup forms a ball in the ice water that melts away if you try to pinch it with your fingers, you've reached the appropriate temperature.