Walnut Cake with Coffee Frosting
This incredible walnut cake has layered soft, delicious yellow sponge cakes soaked with a flavorful rum syrup for an extra moist dessert. Roasted walnuts add a crunch and taste that works perfectly with rich coffee icing.
Walnut Cake Recipe
This walnut cake recipe is one that I’ve made often through the years. Admittedly, it isn’t exactly a cake that can be thrown together in 30 minutes. However, good things take time, and this incredible dessert is no exception.
There are several components to this walnut cake recipe, but each one is essential because it brings something crucial to the flavor profile. The entire dessert is a perfectly balanced treat that will make you the most popular person at whichever party you bring it to!
Just follow the instructions I lay out for you below, and I promise—you can absolutely make this walnut cake recipe!
Coffee Walnut Cake
Let’s talk about the flavor profile for a minute. It’s hard to think of a flavor combination I like more than coffee and walnuts. I know that may seem a bit random, but I promise you it’s way better than peanut butter and jelly or any other duo you can think of!
Don’t imagine that you can simply chew some walnuts and sip coffee and get the experience I’m talking about, however. What makes this coffee walnut cake so irresistible is that the walnuts are roasted, which brings out those rich notes and mellow flavor profile that pairs perfectly with acidic coffee.
If you have never tried coffee frosting, you’re missing out big time! In fact, I’ll often make this buttercream to go on top of a simple cake if I’m in a rush. I’ve tried a lot of icings over the years, and this coffee frosting is still one of my favorites!
Although it’s very easy to make, buttercream frosting can be a bit temperamental. If you’re new to the world of buttercream icing, there are a few tips and tricks you need to know to make sure you nail the perfect coffee frosting.
Tips for Getting the Perfect Coffee Frosting
- Buy whipping cream. I often have people ask if there’s a big difference between heavy cream, whipping cream, and whole milk. Each one has a different fat percentage upon which the whipping ability of it depends. Heavy cream will give you the best volume and will hold up the fluffiness of the cream the best.
- Use instant coffee. Make sure to use instant coffee in this recipe, not normal coffee grinds.
- Chill the bowl and whisk. The frosting needs to be kept cooled as you are making it, and one of the easiest ways to do so is to stick your metal mixing bowl and whisk attachment in the freezer for 5-10 minutes before whipping your icing.
- Sift your cocoa powder. Sifting will break up any clumps in the cocoa powder while aerating it, ensuring the most accurate measurements as you are making this walnut cake.
Rum Soaked Cake
Don’t worry—just because this is a rum-soaked cake doesn’t mean that kids can’t enjoy it. If you prefer this cake to be alcohol-free, just substitute the rum with rum flavoring which contains no alcohol.
As a side note – with only a couple tablespoons of rum in the whole cake, there’s no worry about getting drunk on a slice of cake.
The reason there is rum in this recipe is that it adds a rich, buttery flavor to the cake layers. It also adds even more moisture to this cake, without making it soggy.
The easiest way I’ve found to add rum to the walnut cake is to mix it with water and sugar (as noted below in the recipe card), then add it into a squeeze bottle. Drizzle it over each of the yellow cake mixtures, and you’ve got an incredible rum-soaked cake!
More Cake Recipes:
Walnut Cake with Coffee Frosting
This walnut cake has moist layers of rum-soaked yellow cake nestled between rich coffee frosting. Roasted walnuts add crunch, flavor and presentation to this incredible dessert.
Yellow Sponge Cake
- 8 oz heavy whipping cream (at least 33% fat content)
- 2 tbsp Instant Coffee or 2 Via Starbucks packet
- 1/4 cup cocoa powder, sifted
- 12 oz unsalted butter room temperature (12 oz= 1 1/2 cups)
- 1 1/2 can dulce de leche (1 can = 14 oz)
- 1 cup sour cream
- 8 coffee beans (to add to the piped stars on top)
- 4 cups walnut halves (for adding between the layers and for pressing against the sides of the cake)
Bake the yellow cake: Bake the 2 portions of the Yellow Sponge cake according to directions (the ingredients listed above are for 2 portions). Allow to cool completely.
Then using a long serrated knife (I use this one, then I use these knife fixators to help with making perfectly leveled layers), cut the cakes horizontally into 8 thin layers total. Set the bottoms of 2 cakes aside. They will make up the top and bottom of the finished cake.
Using a cake lifter like this one makes it easy to transfer delicate, thin layers from one place to another.
Roast nuts: On a baking sheet roast 4 cups of walnuts at 325F for 20 minutes. Toss every 5 min to prevent burning. Allow to cool, then chop into pieces. Sift the chopped nuts through a large-holed sieve to remove the tiny pieces, leaving the larger ones behind. Use the sifted tiny pieces for something else, we won't need them for this recipe.
Make the syrup: Mix together 1/2 cup sugar, 3 tbsp Bacardi Rum and 1 1/2 cups water for the syrup until the sugar is dissolved. Pour it into a squeeze bottle if available and set aside. Otherwise, you can use a pastry brush or a spoon to soak the cake layers.
How to make the Coffee Cream Filling
Whip the heavy cream: In a well-chilled bowl whip 1 cup of whipping cream with 1/4 cup of sifted cocoa powder and 2 tbsp instant coffee or 2 Starbucks Via packet until stiff peaks, about 4 minutes. Watch the cream closely because it goes from stiff peaks to overwhipped very quickly. If the cream is overwhipped and starts to separate, add a couple of tablespoons of liquid heavy cream and carefully fold until it is no longer chunky, but instead smooth. Refrigerate until needed.
Whip butter & combine with other ingredients: Whip 12 oz room temperature butter in a stand mixer for about 5 minutes or until pale in color and very fluffy, scraping down the sides often. Add 1 1/2 cans of dulce de leche in two additions and whip until combined and fluffy. Carefully fold in the sour cream, then fold in the refrigerated whipped cream.
How to layer the Coffee and Walnut cake
Reserve cream: Reserve and refrigerate 2 cups of frosting. This will be used for the outside of the cake and decorating.
Layer the cake: Now, spread a dab of frosting onto the middle of the serving platter. Place one of the bottoms of the split yellow cakes bottom side down on top and press to adhere. Drizzle or brush on some sugar syrup, then add 1/7th of the coffee cream filling and spread into an even layer. Sprinkle with couple tablespoons of the chopped, roasted walnuts. Top with the next cake layer and press firmly to adhere.
Finish the layering: Continue layering the cake in the manner described above, finishing with the upside-down bottom layer that we reserved earlier. Soak the top with the remaining syrup, then cover the whole cake in a thin layer of the coffee cream using some of the reserved 2 cups from the fridge.
Press the remaining roasted and chopped walnuts all over the sides of the cake.
Pipe Stars: Now add the remaining coffee cream to a pastry bag fitted with a large star tip and pipe 8 stars around the border of the cake. Add 1 coffee bean inside each piped star. Use any remaining chopped walnuts to sprinkle on the inside perimeter of the piped stars. Refrigerate the cake for 12 hours or overnight before serving.