A double barrel cake is an extra tall, elegant, impressive cake. It serves a crowd and there's lots of space on those very tall sides of the cake for you to use all sorts of cake decorating techniques.
In this tutorial I'll show you:
how to prepare cake layers for a double barrel cake
how to assemble a double barrel cake so that it's stable
how to crumb coat and frost it
some decorating ideas for double barrel cakes
How to prepare cake layers for a double barrel cake
You'll need a lot of cake to make such a tall cake. I don't recommend baking your cake layers any taller than normal because with that much batter they won't bake evenly. The outer edges will be over-baked and dry and the centers will be under-baked. Instead, to make a cake twice as high as normal, bake twice as many layer. You can divide them in half with a serrated knife to make space for more filling and more flavour. I'm using my Very Vanilla Cake recipe for these layers:
How to assemble a double barrel cake
To assemble a double barrel cake, layer the cakes and filling like you would for any other cake. You can spread the filling and frosting onto the cake but it's much quicker to use a piping bag. You don't need a piping tip for this! Just cut the end off a piping bag and pipe through that hole.
Use a dot or blob of your frosting to attach the first layer of cake down onto the cake board. Then pipe or spread on your first layer of filling. This is my 4 Minute Buttercream:
You'll need a cake board at least two inches wider than your cake layers. It needs to be a thick or strong material like acrylic or foam core. Cardboard isn't ideal because double barrel cakes are heavy and if your cake board isn't strong enough it will buckle when you lift it. Alternate cake and filling, finishing with cake on top before your cake reaches six inches tall.
How to stack a double barrel cake so that it's stable
At this point you're going to need supports before putting any more layers onto the cake and adding more height. You can either use boba straws, which are wider and thicker than regular straws or you can use dowels. Poke one in two inches from the edge of the cake and push it all the way down to the bottom of the cake. You'll feel it hit the cake board at the bottom.
Pinch the straw where it sticks out above the cake, which is the exact height of the cake.
Cut it at that point. Then hold it up against your other straws or dowels and cut them so that they're all the same height.
Push the first straw back into the hole you made at the beginning. Then place the other ones around the cake so that they're all at least two inches in from the edge of the cake. They also need to be at least two inches apart from each other. You'll need four straws for small cakes like this six inch cake or you'll be able to fit more in if your cake is bigger.
Spread some buttercream or ganache over the top of the cake to make it sticky and then press another cake board down on top. Notice this hole in the middle which is very useful for later. This cake board should be the same size as the cake but if it's bigger you can trim it. The reason you want it to be the same size is that after you've frosted this cake you want the cake board to be invisible, not sticking out through the frosting.
Continue layering your cake and filling on top of this cake board. Don't make this second part of the cake any taller than six inches either. Now use your offset spatula to spread around the sides of the cake to flatten any filling sticking out.
Use a central dowel so that the top cake doesn't slip or slide sideways. Push it down through the top tier and you'll feel it hit that circle on the cake board in the middle of the cake. Keep pushing until you feel the bottom cake board below the cake. Mark the dowel at the top where it sticks out above the cake and then pull the dowel out.
Use something like wire cutters to cut it where you made that pencil line. You can buy these dowels at craft stores or cake shops. Then push it back in and it will hold your cake straight and prevent any cake layers from sliding sideways.
How to frost a double barrel cake
I definitely recommend chilling this before frosting it because the cake will be a lot less wobbly when it's cold. Putting the cake in the fridge for 30 minutes to an hour is ideal. You'll need a crumb coat before you do your final coat of frosting to prevent crumbs in your final coat. Don't take too much time to get this frosting perfect! What's important is that the sides of the cake are straight and the top of the cake is level.
Put the cake in the fridge for another 30 minutes to set this crumb coat. When it's firm, spread on another layer of frosting. For this layer, take your time to get it as smooth as possible because this layer will be visible.
Frosting such a tall cake is tricky because it's a huge surface to get perfectly smooth. If this is your first time and if you haven't perfected your technique for smooth frosting I recommend a cake design that uses either lots of piped texture to decorate the cake, which will help you cover up any imperfections, or added details like figures or wafer paper or or strategically placed sprinkles.
It's easiest to use a cake comb at least as tall as the cake. After a few scrapes around the cake, spread some more frosting over any indents or areas you need to touch up. Then scrape around the cake again until the frosting is really smooth. With a tall cake comb, each scrape around the cake smooths the entire side surface of the cake. This will give you the straightest and smoothest sides.
To level out the uneven frosting around the top edge, push sideways with your offset spatula. Alternatively, put the cake back in the fridge until the frosting has set and then use a hot sharp knife to slice it off.
Decorating ideas for double barrel cakes
Now it's time to decorate the cake. I refrigerate mine to set this final layer of frosting first. Then I spread bands of coloured frosting over the top and scraped them to leave a thin layer left behind.
Because the frosting is very cold and firm, as I spread and scrape off each layer of colour, that colour sets before I spread and scrape the next layer. This means they don't blend together and that's how I get this layered colour effect.
Since double barrel cakes are so tall and impressive, I like to use minimal decorations. On this cake I used an artificial flower and some macarons and golf leaf.
And that is how to assemble and frost and decorate a double barrelled cake! You might be wondering how on earth to serve this and it's much more straightforward than you'd imagine. Slice the cake and you'll feel when your knife hits that cake board in the middle of the cake. Cut all of the slices of the top half as normal.
I like to cut around the central dowel but if you like, you can pull it out before you start. Then lift the middle cake board up and cut the bottom half of the cake.
I hope I've answered all of your questions about double barrelled cakes! If there's anything I've missed please put your question in the comment section below. Visit my cake school to learn hundreds of cake decorating techniques and designs. I hope to see you there!