Oh my goodness, I can't even begin to describe how delicious this cake was for my little girl's 10th birthday. A light vanilla sponge, chocolate ganache and marshmallow vanilla frosting - it was beautiful and scrumptious. Nothing about this cake is difficult to make, but it does require a bit of time to allow things to cool before assembling. My daughter wanted a chocolate and vanilla cake, but left the details up to me (I love when they do that). The coconut flour in the batter gives the wonderful moistness to the sponge in lieu of the more traditional almond flour used in opera cakes. The ganache is rich but lovely in thin layers throughout the cake. And just a bit of marshmallow fluff in the frosting lightens up the buttercream parts. A proper opera cake uses a coffee sugar syrup brushed onto each sponge layer, but I created a simple cocoa-sugar syrup which worked perfectly. It was such a beautiful cake, too. We were so excited cutting and serving the cake we almost forgot to sing! Enjoy!
Side view of the beautiful opera-style cake for my daughter's birthday.
My cursive G leaves much to be desired, but Gwen was very happy with her cake.
A beautiful slice for the birthday girl!
Opera-style Cake
Makes a cake approximately 6" x 8"
Sponge Cakes:
Preheat the oven to 350 F. Butter the edges and line 2 quarter sheet baking pans with parchment paper (quarter sheet baking pans are approx 8x12 inner dimension or 9x13outer dimension metal cookie sheets - I LOVE this size. Perfect for the toaster oven, and perfect when you have multiple things you want to roast separately in the regular oven, and of course, opera-style cakes!)
In a large bowl, whisk together:
1/2 cup coconut flour
1/2 cup white rice flour
1 cup sugar
1/2 tsp baking soda
1/2 tsp salt
Add and whisk in until smooth:
1 cup milk
1/2 cup oil
6 large eggs
2 tsp vanilla bean paste or vanilla extract
Divide between the two parchment-lined pans. Bake at 350 F for approximately 15-18 minutes. These are nice and thin, so they cook quickly. They should look lightly browned on the edges and no longer wet in the center. Depending on your oven, they may need an extra minute or two.
Remove from oven. Let rest 5 minutes before flipping onto cooling racks to cool. Once cool, carefully slice each cake in half so you'll have four even layers for your cake.
Cakes fresh from the oven - a lovely pale gold with light browned edges
Each of the cakes were sliced in half, so there are four even layers.
Ganache:
Once cakes are set to cool, prepare your chocolate ganache. It will need some time to cool a bit on the counter before assembling the cakes, so timing-wise, I found this worked well.
In a saucepan over medium heat combine and heat until bubbling gently:
1/2 cup butter
1/2 cup whole cream/whipping cream
1/2 tsp vanilla bean paste or extract
Remove from heat and stir in until smooth (this takes a bit of patience, usually a few minutes):
8 oz high quality semi-sweet or bittersweet chocolate chips (or bars chopped well)
Once the ganache is nice and smooth, you can divide it into a couple bowls so it will cool down a bit faster. If you use it right away, it'll just pour off and be too thin. I prefer to let it cool down sitting out on the counter rather than in the refrigerator. But if you're in a bind, you can help it chill faster by placing it in the refrigerator.
Chocolate-Sugar Syrup:
(This is in place of the traditional coffee syrup - which is coffee mixed with sugar - the cocoa powder gave a perfect bitterness to the syrup so it worked wonderfully to brush on the cake layers!)
In a mug, combine:
1/2 cup boiling water
1 Tbsp cocoa powder
1/4 cup sugar
Stir until sugar is completely dissolved and you have a nice, smooth sugar syrup to use to brush on your cakes.
Vanilla-Marshmallow Frosting:
Once cakes have cooled, you can prepare your frosting, as it's time to assemble!
Beat together in a mixer until light and fluffy - 2-3 minutes:
1/2 cup butter, softened
1 1/2 cup powdered sugar
1/4 - 1/2 cup marshmallow fluff
1/2 - 1 tsp vanilla extract
1 - 2 tsp (or more if needed) cream or milk
Assembling your cake:
To assemble cakes:
1. Brush each cake layer with your chocolate-sugar syrup
2. Spread one layer with 2/3 of the frosting. Spread the remaining frosting on one layer (this will be your top layer).
3. Gently spread some chocolate ganache on top of the two layers that have no frosting. Then, spread the chocolate ganache on top of the layer with 1/3 icing (your top layer). *You may have to add a second layer of ganache to some areas if it spreads too thin. The ganache should be warm enough to spread and give a beautiful sheen to your layers. If the ganache isn't warm enough, you can gently heat for 10 seconds in the microwave to warm it up. I didn't use all my ganache and had some leftover. You do want some extra saved in order to pipe decoration on the top. I also had a tiny bit of extra frosting left, so I spread that on top of one of the ganache layers - since extra frosting is always nice.
The far cake has just been brushed with the chocolate sugar syrup. The front was brushed with the chocolate sugar syrup, then had some frosting and ganache spread on top.
Covered layers, ready for their brief refrigeration. I did spread a little extra frosting I had on top of one of the ganache layers.
4. Place the frosted/ganache covered layers in the refrigerator for 10-15 minutes.
5. Remove from the refrigerator and pipe decoration onto the top layer using ganache in a ziploc bag with the corner snipped off, if desired. For a proper opera cake, they write the word "opera" in beautiful cursive. I wrote "Gwen", since it was my daughter's birthday. You want to pipe everything before it sets, although I did add an extra layer of ganache on top of the original "Gwen" so it would stand out a little extra for the birthday girl. 
If you pipe warm (not hot) ganache onto slightly cooled, but not set ganache, you can end up with a beautiful look that defines the top of most proper opera cakes. I added an extra layers to make her name really stand out, but it looked very pretty before I added that layer.
6. Carefully, assemble your cake as desired (I prefer to assemble on a wire rack and then slide it onto the platter, but you can assemble it on a platter and slide strips of parchment paper under each side to remove after you're done assembling and cutting. I like to assemble in the following order: Bottom - all ganache, Second to bottom - all frosting, Third layer - all ganache, and then the top layer with your decoration.
7. Refrigerate another 15 minutes. *I find if you refrigerate it too long, you'll lose the beautiful sheen because the ganache sets too hard. Although it does tend to warm up and still look nice once it's left at room temperature.*
8. Using a large knife (you can heat it if you like, but I found just wiping it well with a paper towel between slices worked for me), slice off the edges to create the clean, beautiful edges that define a proper opera cake. 
Edges being sliced clean. No one complained about having to taste-test the cut-off edges.
It looked so pretty!
9. Carefully slide the cake onto your prepared serving platter OR remove the parchment paper pieces. Try to touch it as little as possible on the top to avoid messing up the beautiful sheen. Leave at room temperature until serving. Serve in thin slices or small squares to show off your pretty layers! Yum!
This cake is best served at room temperature and made on the day you're serving because of the beautiful shine on the ganache. However, leftover cake stores perfectly sliced in the refrigerator in tupperware - and it tastes just as delicious a day or two after assembling. You could even freeze slices, let them defrost in the bag and then serve at room temperature as well for leftovers! Enjoy !
A birthday cake to remember!
