Hello, friends! Another party cake? Absolutely. So what makes a cake a party cake exactly? Well, technically I think any layer cake could be considered a party cake, but maybe it's the presence of sprinkles that warrants the name? Must be. Must be the sprinkles. Or maybe it's the glossy swirls of frosting. Or in this case, the heaps of Belgian milk and dark chocolate transformed into a chocoholic's dream. Come to think of it, I don't think you need a party to enjoy a party cake. Either way, this cake is party-ready and really all about the chocolate. We fill and frost three layers of decadent dark chocolate butter cake with the swirls of one of the most glorious chocolate fudge frostings I've ever tasted and let the chocolate shine. 
What I love about this frosting, aside from how quick and easy it is to make, is that it really isn't very sweet--think more fudgey and decadent--since premium chocolate is the main ingredient. I add a dollop of sour cream to add a creamy richness, and only a small bit of confectioners' sugar to balance out the chocolate. We use mostly milk chocolate this time, though, as opposed to my much-loved dark chocolate frostings (like this intense and wonderful glossy dark chocolate frosting), which results in a dessert simple enough to please cakelets aplenty and decadent enough to please adults alike. 
The cake itself if a version of this moist dark chocolate cake made with butter, dark cocoa powder, and a hit of mayonnaise for moisture, among other cakey ingredients. It takes a few moments to make than our beloved one-bowl chocolate cake recipes, but has a richness only butter can bring to the table. Smother it all in this chocolate lovers' dreamy frosting and a medley of happy-happy sprinkles, and it's definitely a party. 
Yes, it's official--it's a party! And here's a little random side-note: I cannot stop buying vintage birthday candles. Between ebay, etsy, and junk store shopping, I'm always on the lookout and each one is such a treasure. My collection is growing and just looking at these quirky little boxes makes me happy. As does this cake. So, let's make this cake! 
Double Chocolate Party Cake
Decadent chocolate butter cake filled and frosted with a rich, creamy and not-so-sweet chocolate fudge frosting and topped with a medley of sprinkles.
For the Chocolate Cake Layers:
- 1 1/2 sticks (170 g unsalted butter, softened)
- 1 3/4 cups 450 g packed light brown sugar
- 2 teaspoons 10 ml pure vanilla extract
- 3 eggs (at room temperature)
- 1 3/4 cups 220 g all-purpose flour
- 3/4 cup 90 g Dutch-process dark cocoa powder
- 1 1/2 teaspoons baking powder
- 1 teaspoon salt
- 1 1/3 cups 320 ml buttermilk, room temperature
- 1/4 cup 60 ml mayonnaise
- 1 teaspoon baking soda
- 2 teaspoons 10 ml white vinegar
For the Chocolate Fudge Frosting:
- 1 1/2 cups 340 g unsalted butter, softened
- 1/2 cup 60 g confectioners' sugar, sifted
- 1/2 cup 60 g dark cocoa powder, sifted
- 1/3 cup 80 ml hot water
- 1/4 cup 60 ml sour cream
- 1 teaspoon pure vanilla extract
- 1/8 teaspoon salt
- 10 ounces 290 g milk chocolate, chopped, melted and cooled slightly
- 5 ounces 150 g dark chocolate, chopped, melted and cooled slightly
- Sprinkle medley (for decorating (see Sweetapolita's Notes))
For the Chocolate Butter Cake Layers:
- Preheat oven to 350° F. Spray three 8-inch round cake pans with cooking spray and line with parchment rounds.
- In a stand mixer fitted with the paddle attachment, beat the butter, brown sugar and vanilla on medium-high speed until pale and fluffy, about 7 minutes. Lower the speed to medium and add the eggs, one at a time, mixing until each is fully incorporated before adding the next.
- Sift the flour, cocoa powder, baking powder, and salt into a medium bowl.
- Lower the mixer speed to low, and alternate dry ingredients and the buttermilk into creamed mixture, beginning and ending with dry ingredients (dry, wet, dry, wet, dry). Mix until just incorporated, then fold mayonnaise into batter with a whisk, until just blended. In a small bowl, combine the vinegar and baking soda (it will foam) and quickly add to batter, mixing until just combined.
- Divide the batter evenly between the prepared pans. If possible, weigh the batter in each cake pan for 450 g each (excluding the pans--you will want to tare the scale each time.) Smooth the batter with small offset palette knife, and bake the first 2 layers until a toothpick or skewer comes out clean, about 25 minutes (don't over-bake). Let pans cool on wire rack for 20 minutes, then invert cakes onto racks, gently, peeling away parchment rounds. Repeat with the final layer. Let cool completely.
For the Chocolate Fudge Frosting:
- In a bowl of stand mixer fitted with paddle attachment, beat the butter on medium speed until pale and fluffy, about 6 minutes. Reduce to speed to low, and add the confectioners' sugar, cocoa powder, water, sour cream, vanilla, and salt and beat until incorporated, about 1 minute. Increase the speed to medium and beat for 2 more minutes.
- Add the melted chocolate and beat on medium speed until smooth, about 1 minute.
Assembly of the Double Chocolate Party Cake:
- Put your first layer top-up on the cake board or plate, and spread about 1 cup of frosting evenly across layer. Put the second cake layer on top and repeat with another layer of frosting. Put the final cake layer top-down. Cover the cake with plastic wrap and wiggle the layers into place, if necessary. Refrigerate the cake until firm, about 30 minutes.
- Remove the cake from the refrigerator and place on a turntable, if using. Frost entire outside of cake with a thin layer of frosting to seal in the crumbs. Chill until the frosting begins to firm-up, about 15 minutes. Use the remaining frosting to create a textured finish by spreading with a medium palette knife.
- Cover the perimeter of the cake with a medley of sprinkles (see Sweetapolita's Notes) and serve. The cake will keep at room temperature for up to 2 days, refrigerated for up to 3 days. Best enjoyed at room temperature.
- For the chocolate cake I used, yep--you guessed it--Cacao Barry Extra Brute
cocoa powder. I keep this stuff on hand at all times and use it for everything from brownies to hot chocolate. Completely decadent and completely worth it.
- For the frosting, I used Callebaut Milk Chocolate Callets
(this chocolate is also amazing for chocolate bark and the like) and Callebaut Semi Sweet (Dark) Callets
semisweet chocolate.
- To frost and create a wide "swirl" texture, I use a medium Wilton Palette Knife
and the Ateco Revolving Cake Stand
.
- For the sprinkle medley you can use any party-ready sprinkle medley! Some of my favourites are Bright Skies, Birthday Party, or Hey, Sugar!
cocoa powder. I keep this stuff on hand at all times and use it for everything from brownies to hot chocolate. Completely decadent and completely worth it.
(this chocolate is also amazing for chocolate bark and the like) and Callebaut Semi Sweet (Dark) Callets
semisweet chocolate.
and the 
.
