With a half and half cake you can offer two completely different flavours in just one cake! They’re great for joint birthday celebrations or just to give people two different options.
How to prepare layers for a half and half cake
You’ll need two or four layers. Any even number will work, depending on how tall you want your cake to be. I’m using two marble layers for one half and for the other half, chocolate and banana layers.
Both halves of the cake need to be the same height to make a level cake. Before assembling, stack the layers to see if one side of the cake would be taller than the other. Use a serrated knife like a bread knife to trim any taller layers. Now cut all of the layers in half down the middle.
Prepare your filling and frosting for each half of the cake. I’m using Nutella and dulce de leche for fillings and also mixing them into my 4 Minute Buttercream for the frostings.
How to assemble a half and half cake
The easiest way to assemble your cake is to put some frosting into a piping bag with the tip cut off. If you don’t have a piping bag you can spread it on instead.
Spread or pipe two dots of frosting onto a cake board. Push half a cake layer into one dot to attach it to the board. Then spread or pipe frosting along the cut edge and press another half of cake into it. It will attach to the cake and to the other dot of frosting on the cake board.
If your fillings are runnier than buttercream you'll need what’s called a buttercream dam. This is a wall around each cake layer to hold in the filling. It prevents the filling from oozing out from between the cake layers. On the chocolate and banana layers I spooned dulce de leche into the dam. Nutella made the perfect filling on the Easy Marble Cake half.
In hindsight I wish I’d chosen flavours that looked more obviously different than these! The chocolate and banana layers are almost the same colours as the chocolate and vanilla marble.
Place the next layers on top to continue assembling your cake. The frosting along the cut edge of each layers is really important. It attaches the two sides of each layer together, otherwise the cake can split down the middle and fall apart. This frosting acts as glue to hold them tightly together.
Push the two halves of the cake to stick them firmly together and also push down to level the cake.
How to frost a half and half cake
Divide the rest of your frosting into two bowls and add any frosting left in your piping bag, too. Tint each half with a different colour or use different flavour ingredients for each bowl.
Spread a few dots of frosting onto one half and wrap that half with parchment paper. The parchment will stick to the dots. Trim the parchment so it covers only that one half of the cake. Then use the other flavour of frosting to frost the exposed side of the cake. The parchment will prevent that frosting from getting onto the covered half.
It's always a good idea to apply a crumb coat of frosting first. This will trap any crumbs that come off the cake so they don't get into your final layer of frosting. It’s messy but that’s fine because it will be covered up in a minute.
When you peel the parchment off, the frosting will stop exactly in between the two halves of the cake!
Do the same for the top, covering up the other half of the cake with parchment before spreading frosting onto this half.
Then cover up the frosted side of the cake with parchment paper. Spread frosting onto the other half of the cake. Optionally, you can chill the cake before you do this. If you don't, when you peel the parchment off you’ll leave some texture behind on the frosting. Since it’s just the crumb coat (which will be covered up) it doesn’t matter.
Put the whole cake into the freezer for 15 minutes until the frosting has set. To test it, touch it and check that you don't leave any texture in the frosting. Some tiny condensation drops will form on the frosting, which will help parchment stick as you cover up one half.
Spread frosting onto the other half. Apply the frosting more thickly now because this is the final layer of frosting so you want it to be much neater than the crumb coat. Scrape around this half of the cake with a frosting comb to smooth the frosting. Then tidy up the top edge of the cake by swiping the frosting sideways with your offset spatula. Peel the parchment off to reveal a neatly half-frosted cake!
Put the cake back in the freezer for another 15 minutes to set this frosting. Then repeat the process for the other half of the cake, covering this side with parchment and then spreading another flavour of frosting onto the other side. Because the first flavour has set, pressing parchment against it won’t imprint any texture into the frosting. When you peel it off the frosting underneath will look perfect!
Half and half cake decoration ideas
The joins between the flavours are fairly neat but I always like to cover mine with something. For this cake I’m piping some details with two tone frosting, which is easy to make! Fill a piping bag with one flavour on one side and another flavour on the other side. I like to put the piping bag into a glass to hold it open for this.
Then push both flavours down to the piping tip. This is a 1M star tip. These swirls or rosettes hide the join of the two flavours of frosting, and also add some pretty details. If you don’t want to blend the flavours of the two halves, pipe with plain vanilla buttercream in different colours.
Why make a half and half cake?
A half and half cake is a great way to use up extra layers. You might be wondering, "why would I have extra cake layers?" Maybe your batter didn’t make enough to make the size of cake you were planning on. Maybe it made too much so you have one too many cake layers for your cake. In my case, I bake in bulk so I have loads of layers in the freezer to pull out whenever I want to make a cake. Sometimes I’ll end up with one lonely banana or chocolate layer, like these. They're perfect for a half and half cake!
People are always blown away by half and half cakes and excited to see the inside. Although I wouldn’t serve anyone a piece this big, it’s fun to show off the two flavours within one slice!
The possibilities for this are endless - wouldn't it be a fun idea for a wedding cake?! For birthday cake ideas and designs for every occasion visit my online cake school.