This number cake features moist lemon layers, tangy blackberry mousse, and sweet vanilla buttercream, creating a wonderfully balanced flavor profile. It's a beautiful, fresh, and festive cake that’s perfect for any celebration!
Number Cake for a Special Birthday
To celebrate my big 3-0, we threw a fun dinner party. With my belly just as round as my age (thanks to nearing the third trimester), I stuck to alcohol-free cocktails, but that didn’t stop me from celebrating! My husband, Martin, went all out and arranged an incredible Asian-themed dinner with all my favorite dishes: sushi, gyoza, skewers, and spring rolls. And of course, there had to be an amazing cake – so I made it myself! 😉
I’m not one of those people who dread turning 30 – quite the opposite! So, I decided to bake a number cake to show off my lovely number front and center. I wanted something fresh and light, so I went with a lemon cake paired with blackberry mousse, topped with fresh berries. The result was delicious, festive, and even though our guests were stuffed from the meal, there was barely any cake left!
What is a number cake?
A number cake—or letter cake or alphabet cake– is a cake shaped to display the number being celebrated. This fun trend has become increasingly popular in recent years, and the creative opportunities here are endless! Number cakes can be made from a single cake, like this chocolate number cake or this lemon number cake, or they can have multiple layers like this amazing raspberry number cake. While it does take a bit of patience to cut and decorate a number cake, the effort is definitely worth it because it’s hard to find a cake more festive than this!
Number cakes can also be made as a layer cake using buttercream or mousse. I love the perfect edges that’s possible to achieve with a mousse, plus I love the texture that mousse gives to a cake—it makes it so light that you get the sensation of thinner layers with a silky smooth center. And making a layer cake number cake with mousse is actually pretty easy! It simply requires some extra time for the mousse to set.
For my number cake, I chose a tangy blackberry mousse. I love the beautiful purple-pink color that the dark berries give to the mousse, and the flavor pairs perfectly with the lemon cake layers. The tangy cake is complemented by the sweet whipped vanilla buttercream piped on top.
Can I Make the Number Cake Ahead?
This number cake has a lot of elements, so it’s helpful to prepare some in advance. Here are my tips on how to plan ahead:
You can bake the cake layers, assemble them with mousse, allow it to set, and then cut your number cake—before freezing it for up to 3 months. Let the cake thaw in the fridge the night before serving.
Meringue kisses can be baked up to 2 weeks before decorating the cake, as long as they’re stored in an airtight container. They can also be frozen for up to 2 months.
Fondant flowers can be made several months in advance. Let them harden uncovered, and once they’re completely dry, store them in a plastic container to keep them dust-free.
By following these tips, all you’ll need to do on the day of serving is whip up the buttercream and decorate your cake.
How to Bake and Cut a Number Cake
This number cake features lemon-flavored sponge layers and a tangy blackberry mousse. The lemon cake is baked in an adjustable square baking pan and then sliced into two layers once it has fully cooled. If you’re making two number cakes like I did, you’ll need to bake two lemon cakes, giving you four layers in total. It’s best to prepare the batter for each cake separately, so mix and bake one at a time.
After the lemon cake has cooled, slice it into layers using a serrated bread knife. Gently cut all the way around the cake, gradually slicing deeper until you’ve cut through the entire cake. The layers should be about 1 cm (1/3 inch) thick.
The cake’s filling is a blackberry mousse, which should be made the night before serving (unless you’re freezing the cake, as mentioned above). If you’re making more than one number cake, feel free to double the mousse recipe.
To assemble, place the bottom cake layer with the cut side facing up on the serving dish or board. Tighten the adjustable baking frame around it. Prepare and spread the blackberry mousse evenly over the layer. Place the top cake layer on top, again with the cut side facing up, and press down gently. Let the cake set in the refrigerator for at least 6 hours, preferably overnight.
Now for the fun part! Once the mousse has set, it’s time to cut out the number. You can either print or draw a template to guide you, or be bold and freehand it. Cut along the inside edge of the adjustable baking frame before removing it. Place the template on the cake and carefully cut out the number with a sharp knife, removing excess cake as you go until only the number remains on the serving dish.
Clean up any mousse or crumbs from the dish, and chill the cake for at least 30 minutes before decorating so the mousse firms up again.
Tips for Decorating Your Number Cake
You can decorate your number cake however you like. If you want to replicate my design, here’s what I used:
This beautiful number cake features lemon layers and tangy blackberry mousse. It’s decorated with buttercream, meringue kisses, fresh berries, and flowers – sure to make any birthday celebration extra special!
Preheat your oven to 180 °C (356 °F). Prepare an adjustable square pan (23x33 cm / 9x13 inches) by lining it with parchment paper – place the paper under the pan and fold it up around the sides, securing with paper clips. If you don’t have an adjustable pan, you can use a square pan of a similar size, but be sure to grease it thoroughly.
Melt the butter and let it cool slightly. Meanwhile, mix the flour and baking powder in a bowl.
350 g butter, 300 g flour, 1 ½ tsp baking powder
In a separate bowl, beat the sugar and lemon zest together with a hand mixer on high speed until the zest is well incorporated. Add vanilla, lemon juice, eggs, and melted butter, and continue mixing at medium speed until well combined.
350 g sugar, Zest from 3 lemons, 2 tsp vanilla, 4 tsp lemon juice, 6 eggs
Gradually add the flour mixture to the wet ingredients, stirring gently with a spatula until you have a smooth batter.
Pour the batter into the prepared pan and bake for 30-35 minutes, or until golden brown. Test the cake’s doneness by inserting a toothpick – it should come out clean when the cake is done.
Let the cake cool completely in the pan until it reaches room temperature.
Once cooled, carefully remove the cake from the pan. For best results, use an adjustable pan that can be easily loosened. If using a regular pan, gently run a spatula around the edges and lift the cake out.
Use a serrated bread knife to slice the cake into two even layers. To do this, score a line along the middle of the cake and carefully cut all the way through. The layers should be about 1 cm (1/3 inch) thick.
Wrap the layers in plastic wrap and refrigerate until ready to assemble with the mousse.
Blackberry Mousse:
Soak the gelatin sheets in cold water for 10 minutes.
3 sheets of gelatin
In a small saucepan, combine the water, blackberries, and sugar. Bring it to a boil, then lower the heat and let it simmer for 2-3 minutes.
1 tbsp water, 250 g frozen blackberries, 3 tbsp sugar
Remove the saucepan from the heat and blend the mixture with an immersion blender until smooth.
Place the saucepan back on the stovetop. Take the softened gelatin out of the water, wring out the excess water, and stir it into the berry mixture until dissolved.
Pour the berry mixture into a bowl through a fine mesh strainer to remove any seeds. Let it cool to room temperature in the fridge.
Whip the heavy cream to soft peaks. Gradually fold in the cooled blackberry sauce, being careful not to let it separate. Once fully incorporated, the mousse is ready to use.
250 ml heavy cream
Italian Meringue Kisses:
Whisk the egg whites with a hand mixer until stiff peaks form.
30 g egg whites
In a small saucepan, combine the sugar and water, heating over low heat until the sugar dissolves.
75 g sugar, 30 g water
Increase the heat to medium-high and bring the sugar syrup to a boil. Let it simmer, stirring occasionally, until it reaches 116 °C (241 °F) on a candy thermometer.
Slowly pour the hot syrup into the egg whites while whisking continuously. Be careful not to splash the syrup!
Continue whisking until the meringue cools to room temperature and stiffens. Stir in the vanilla.
¼ tsp vanilla
Preheat your oven to 100 °C (212 °F) and line a baking sheet with parchment paper.
Transfer the meringue into a piping bag fitted with a small star tip and pipe small meringue kisses (about 2 cm in diameter).
Bake for 30 minutes on the second-lowest oven rack. Let them cool and transfer them to a wire rack to cool completely.
Whipped Buttercream:
Prepare your whipped buttercream as per the recipe above and fill a piping bag fitted with a round tip (about 1 cm).
1 batch of my whipped vanilla buttercream
Assemble the Cake:
Place the bottom layer of the cake with the cut side facing up on your serving platter or board. Tighten the adjustable baking pan around it.
Spread a layer of blackberry mousse evenly over the cake.
Place the second cake layer on top, with the cut side facing up, and gently press down.
Cover the cake with plastic wrap and refrigerate for at least 6 hours, or overnight, to allow the mousse to set.
Cut the Cake:
Print or draw a template of the number you want and cut it out. My “5” in the pictures measures 22x32 cm (9x13 inches).
Place the template on top of the cake and carefully cut along the template with a sharp knife, removing any excess cake.
Clean up any mousse or crumbs from the dish and refrigerate the cake for at least 30 minutes before decorating.
Decorating the Cake:
Decorate your cake however you like. For inspiration, here’s what I used:
Whipped vanilla buttercream
Fresh blackberries
Fresh blueberries
Fondant flowers
Mini meringue kisses
Edible flowers (I used small purple honey flowers)
Notes
*Yield: Makes 1 number cake approx. 23x33 cm (9x13 inches) depending on the number.
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Hi, I’m Trine – home baker from Copenhagen, Denmark. “Bageglad” means happy to bake in Danish and I have been spreading this happiness on the blog since 2012. Today, it reaches more home bakers worldwide than I could ever have dreamed of! Thank you for visiting!
Hi, I’m Trine – home baker from Copenhagen, Denmark. “Bageglad” means happy to bake in Danish and I have been spreading this happiness on the blog since 2012. Today, it reaches more home bakers worldwide than I could ever have dreamed of! Thank you for visiting!
Difficulty: Advanced
Yield: 10 servings*
