Here are 10 number cake hacks for baking, filling, layering, frosting and decorating!
#1 Turn any cake into a number cake
You don't need to buy special molds or baking pans to make a number cake. Instead, just cut a piece of paper so it's the same size as the cake you've baked. Draw your number onto that piece of paper and cut it out. Place it on your cake and cut around it with a serrated knife like a bread knife.
Depending on the size of the number cake that you want to make, you might choose to cut out one or two numbers from each cake. To cut out two, fold the piece of paper in half before you draw your number. This way, the number will be half the size of your cake. Trace the number onto the cake twice to get two layers out of each cake. This is my Perfect Chocolate Cake:
#2 Attach your number cake to a cake board
It's important to attach your number cake onto a cake board so it doesn't slide around. Pipe or spread at least two dots of buttercream frosting onto the cake board. Then lower your cake onto those dots. The buttercream acts like glue to attach the cake and hold it in place.
Now you can layer, decorate, and lift the cake on the board without it moving around. This is my Very Vanilla Cake:
#3 Fix broken number cake layers
Sometimes, cakes crack or break apart as you're lowering them onto the cake board. Use buttercream as glue to attach the pieces back together! Pipe or spread a dot wherever the piece broke off and then press the piece against the dot.
After filling and frosting the cake you'll never know it was broken!
#4 Spacing designs equally
For multicoloured filling, for example a rainbow, you'll want to space the colours evenly across your cake.
Mark out the sections onto your cake by scoring them with a knife before you start piping. I like to start by scoring halfway across the cake. Then divide those sections in half and in half again, as many times as necessary.
It's easiest to carve and assemble cakes when they're cold rather than at room temperature. When they're cold, they're firmer and less likely to crumble or break. To chill a cake, wrap it in plastic wrap and put it in the fridge for an hour or overnight. I like to chill sheet cakes before carving them into number cakes. Next, while they're still cold, move the number cakes onto a cake board and layer them with fillings.
#6 How to frost number cakes with holes
Some numbers have holes in them, for example a number four or six or nine. The easiest way to decorate these number cakes is to leave that hole intact instead of cutting out the hole. When you frost the cake, pipe or spread a different colour over the "hole". This makes it clear it's not part of your number and the number will be recognizable. You'll save time carving and you won't have to frost any tricky areas of cake.
#7 Chocolate collars on number cakes
If you struggle to get smooth frosting on your cakes, I have bad news! It's even trickier to achieve smooth frosting on a number cake. I'll give you tips for this later in #9 but for now, here's a quick hack to avoid smooth frosting. Use chocolate to cover your cake instead!
Start by covering the cake in a crumb coat. This is a very thin layer of frosting that doesn't need to be perfectly neat. It makes it easier to attach the chocolate to the cake.
Then melt chocolate chips in the microwave at 60% power for 30 seconds at a time. Stir until smooth or heat for another 30 seconds if necessary. Cut strips of baking paper, wax paper or parchment paper so that they're as tall as the cake. Pour the melted chocolate on top, spreading it to cover the paper completely.
Then slide your hands underneath the paper, lift it up and press it against the sides of your cake. Pinch any corners to make sure there's a sharp angle there.
You can use a cake comb to press the paper against the cake to attach the chocolate. Then put the cake into the fridge for about 30 minutes before peeling the paper off.
The easiest way to decorate a themed cake is to use figures or toys rather than making chocolate or fondant decorations. Bring a race track cake to life by adding toy cars, like on this number 8 cake. Hot Wheels type cars are the perfect size and after you've washed and dried them, they're perfectly safe to put on top of a cake.
#9 How to get smooth frosting on a number cake
Let's tackle smooth frosting. This is the trickiest way to decorate a number cake. For the best results it's really important to chill your cake before you start. Cold cake gets much firmer and less crumbly than room temperature cake. This means chunks won't break off when you spread on the frosting and you'll have fewer crumbs in your frosting. Like with all cakes, it's a good idea to start with a crumb coat. This is a very thin layer to trap any crumbs that do come off the cake.
Spread frosting over the top of the cake and around the sides and smooth it with an offset spatula or cake comb. This crumb coat doesn't need to be perfect! Put the cake in the fridge to chill and set, which takes about 30 minutes. Then pipe or spread another layer of frosting on top. If there are any holes in your number I recommend starting with those areas because they're the trickiest.
You can frost a number cake using almost any technique you would use on a round cake. This one is going to be a watercolour design. After any holes, I like to do the top of the cake next to get that smooth. Then do the sides, making sure that the frosting sticks up a little bit above the top edge of the cake. This will give you nice sharp angles later.
You can use the side of your offset spatula to smooth the frosting or a cake comb. Make sure you wipe the blade after each scrape so that it's clean when you use it again. This way you won't drag any excess buttercream onto your smooth frosting.
#10 Cake toppers for number cakes
The best time to add toppers to your cake is immediately after piping or spreading your frosting onto the cake. Toppers include chocolates, candies, flowers, sprinkles and figures. While the frosting is still soft and sticky, anything will attach to it. If you wait anywhere between 10 and 30 minutes, the frosting will set and pushing toppers onto the frosting will crack the frosting.
I hope this has been useful and now you have lots of tips to confidently make a number cake! Ask me any questions in the comments below and visit my cake school to learn hundreds of cake decorating techniques and designs.