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Luscious Lemon Mousse Cake – Layer cake perfection

Luscious lemon mousse cake might be the perfect layer cake. Lemon cake with Limoncello syrup, zesty lemon curd and creamy lemon mousse. (Limoncello liquor is optional.)

A lemon layer cake on a glass cake stand.

I am so excited to share this recipe with you! For many years this was the most popular cake flavor for my custom cake business. Once I introduced the Chocolate Chip Cookie Cake the two cake flavors shared top billing.

For the last 5 years I’d say almost half the wedding cakes I sold had two different flavors in the cake; half the servings with the cookie flavor, and the other half with Luscious Lemon Mousse Cake. And this cake is truly luscious!

Yes, this cake is a little bit of a project. But I think it’s totally worth the effort, especially for a special occasion.

If you watch the video you’ll see the entire process. It is sped up, but you can see how easily the whole thing comes together once you have all the components in place.

a lemon layer cake on a glass cake stand

How to make a great Lemon Mousse Cake:

The step that might be the most unfamiliar to non-pastry-chefs is how to “liason” or “temper” the gelatin into the mousse.

Tempering gelatin is similar to the process for tempering eggs into hot milk to make custard.

If you simply poured the warm gelatin into the cool mousse it might immediately set into little rubbery lumps. Definitely not the texture we’re going for here.

By whisking a scoop of mousse into the melted gelatin we bring the two ingredients closer together in texture and temperature. Now we have silky-smooth mousse. The filling is set with just enough gelatin to hold it together when the cake is sliced.

a slice of lemon mousse cake on a glass plate with a fork

The limoncello makes the flavor extra special. Of course, if you can’t or don’t want to do liquor you can leave it out. You can use water to bloom the gelatin.

But even if you generally aren’t a fan of liquor flavors I suggest you give it a try. The limoncello adds a deep lemon flavor without leaving a boozy aftertaste. You can check out this post to see why alcohol enhances flavor.

a partially eaten slice of lemon mousse layer cake on a glass plate with a fork

This cake recipe incorporates several other recipes. There is no need to reinvent my cake and buttercream recipes every time I come up with a new flavor. I just flavor them to whichever cake I’m putting together. All the recipes are linked in the recipe card.

If you want to try making a “Lemon Meringue” variation of this cake, you can ice the cake with Seven Minute Frosting instead of the meringue buttercream. Use a blow torch on the seven minute frosting for a lovely toasted finish.

Watch the recipe video to see how-to make a Luscious Lemon Mousse Cake from start to finish.


If you love great cake recipes, you’ll love my new book: Easy Baking From Scratch: Quick Tutorials, Time-Saving Tips, Extraordinary Sweet and Savory Classics. The book contains over 100 recipes that have been well-tested and are presented in simple, clear language. It’s available now on Amazon.

Want to learn more about how I create my cake recipes? This post has lots of great information about baking science and how to perfect any recipe.

Now that you’ve mastered this spectacular cake, you might want to give this Key Lime Layer Cake a go. It’s another stunner!


If you love this recipe as much as I do, I’d really appreciate a 5-star review.

luscious lemon mousse cake

Luscious Lemon Mousse Cake

Yield: 16-20 servings
Prep Time: 1 hour
Bake Time: 35 minutes
Chilling Time: 4 hours
Total Time: 5 hours 35 minutes

Luscious lemon mousse cake might be the perfect layer cake. Lemon cake with Limoncello syrup, zesty lemon curd and creamy lemon mousse. (Limoncello liquor is optional.)

Ingredients

Cake

Lemon Mousse

  • 3 tablespoons (1.5 oz, 44ml) Limoncello (use water if you want to avoid alcohol)
  • 1 teaspoon lemon extract
  • 1 1/2 teaspoons gelatin powder
  • 1 cup (8 oz, 236ml) heavy cream
  • 2 tablespoons powdered sugar
  • 1 1/4 cups Lemon Curd

Assembly

Instructions

Cake

  1. Mix the cake according to the recipe, adding the zest to the dry ingredients and the lemon extract with the vanilla.
  2. Divide the batter between two 8" pans lined with a parchment round or buttered and floured. Bake as instructed in the recipe. Wrap the cooled layers and chill until firm (I like to bake the cake a day ahead)
  3. When you're ready to assemble the cake, trim the browned edges and domed top off both cakes. Split each cake horizontally so you have a total of 4 cake layers. See how to prep the layers here. Have your syrup and buttercream ready before you begin making the Lemon Mousse.

Lemon Mousse

  1. Place the Limoncello (or cold water) and lemon extract into a microwave safe bowl. Sprinkle the gelatin over the liquid in an even layer. Whisk briefly to combine and set aside to bloom. Whip the cream with the powdered sugar and set aside.
  2. Place the 1 1/4 cups lemon curd in a large mixing bowl and use a spatula to smooth out the curd to break up any lumps. Fold 1/3 of the the cream into the lemon curd until no lumps of curd remain. Fold in the remaining cream until it's about 1/2 way incorporated.
  3. Heat the bloomed gelatin in the microwave in 10 second increments until it's hot to the touch. Working quickly, add a 1/2 cup of the mousse to the warmed gelatin. Whisk immediately until completely incorporated. Pour the gelatin mixture back into the mousse. Immediately whisk until the mousse is smooth and the gelatin is evenly incorporated. If the mousse is very soft, refrigerate briefly to let it thicken before assembling the cake.

Assembly

  1. Fill a piping bag fitted with a star tip with buttercream (or use a disposable bag with the tip cut).
  2. Set one layer of the cake, flat side down, onto a cardboard cake round or a serving plate. Brush the layer generously with the Limoncello syrup. Pipe a ring of buttercream around the edge of the layer to form a "dam" for the mousse. Scoop half the lemon mousse onto the layer and smooth until even.
  3. Gently place the second cake layer onto the mousse, careful not to squish the mousse layer. Brush the layer with syrup and pipe a dam of buttercream. Set aside a 1/2 cup of the lemon curd and scoop the rest onto the layer. Smooth the curd until even (be careful not too press hard or you might squish the mousse layer beneath).
  4. Place the 3rd cake layer, brush with syrup and pipe a dam. Fill with the remaining lemon mousse. Top with the 4th layer, brush with syrup. Set the cake into the refrigerator for about 20 minutes to set the buttercream "dams" and the mousse.
  5. Ice the cake with a thin crumb coat of buttercream. Refrigerate the cake for at least an hour to set the buttercream and allow the mousse time to gel. Ice the cake with a final coating of buttercream.
  6. Use a piping bag fitted with a star tip to pipe a border around the top of the cake. Spread the last 1/2 cup of curd onto the cake. Refrigerate for at least 3-4 hours to make sure the filling is completely set, preferably over night.
  7. Remove the cake from the refrigerator 1/2 hour before serving.

Notes

The cake must be stored in the refrigerator because of the mousse filling. Take the cake out 1/2 hour to an hour before serving to allow it to soften before serving. Leftovers can be refrigerated and the cake freezes very well.

Did you make this recipe?

Please leave a comment on the blog or share a photo on Instagram

Jenny

Tuesday 20th of July 2021

Hi Eileen, As intimidating as this cake looks, it also looks SO amazing, that I think I’m going to try it.... I absolutely have to!! My friend wants a lemon birthday cake, and this looks like the holy grail of lemon cakes! I have one question. (If this was already covered and I missed it, I apologize.) Could you provide the specific (or suggested) measurements for the lemon extract, lemon zest and limoncello that you add to the buttercream? I am a little worried about getting that wrong. Thank you so much! Jenny

Eileen Gray

Tuesday 20th of July 2021

Hi Jenny, I usually use the zest of 1 lemon and a teaspoon of extract. I would start with a tablespoon of Limoncello and add more until you get a flavor you like.

Lindsey Miller

Friday 2nd of April 2021

Hi Eileen! I'm so excited to make this cake for Easter. When making the lemon curd can i use the limoncello to bloom the gelatin instead of water? Also, when you put the butter in with the gelatin is it melted or room temp butter? Will the heat of the lemon and egg mixture be warm enough to melt the butter? Thank you!

Eileen Gray

Friday 2nd of April 2021

YES, to limoncello! The curd is hot enough to melt the butter and gelatin (unless the butter is frozen or super cold).

Harmony Quinn

Wednesday 10th of March 2021

Eileen, I’m excited to be making this cake for my 40th birthday this weekend. I am vegetarian and so hoping you might be able to direct me on a good substitute for the gelatin in the mousse. I used arrowroot starch in the curd and it turned out great. Can I use that in the mouse as well? Any directions on how much and how specifically to do so? Or would you recommend I use pectin, agar agar, or some other thickener? Or would it be fine without the added thickener since the curd is thickened already? Thank you for your help!

Harmony Quinn

Thursday 11th of March 2021

@Eileen Gray, Okay, so as a follow up...the mouse was NOT thick enough...& the buttercream either too warm or just not strong enough to hold it, lol. The first layer was fine. Even the second layer was okay. By the time I started with the third layer though everything started collapsing and pushing out the sides, then sliding off! Lol! It was a disaster unfortunately. Maybe I should’ve refrigerated it between layers, I don’t know. Really though, I think this illustrates the need for both the curd AND the mousse to be quite thick and strong! I do NOT recommend skipping the gelatin/thickener stages! I wish I could attach pictures of the disaster for illustrative purposes. You’d get a good laugh!

Harmony Quinn

Wednesday 10th of March 2021

@Eileen Gray, Okay great, thank you!

Eileen Gray

Wednesday 10th of March 2021

I don't have a great deal of experience with arrowroot or agar agar. I put gelatin in the mousse so it will hold it's shape when the cake is sliced. The buttercream dam will hold the mousse in place until the cake is cut. I think you might be OK without any thickener. The slices might just be a little soft on the plate. In other words, the slice wouldn't be able to stand up the way it is in the photo. But will work find laying on the plate.

KAREN VENDITTI

Tuesday 22nd of December 2020

my buttercream does not seem to be thickening. Is there anything I can do to help it . How long do I whip it for it to come together?

Eileen Gray

Tuesday 22nd of December 2020

If your meringue is not completely cooled or your butter is too warm, the buttercream can be soft. Try refrigerating it until it begins to firm up. Then rewhip it to bring to back to the correct texture.

Betsy Mains

Friday 11th of September 2020

Hi! I'm so happy to find this site. I love baking and appreciate your expertise here. I made this cake yesterday, and when I took it out of the oven, I almost let it cool upside down, but I didn't because I was worried it would fall out of the pan given the parchment. So, it fell a bit in the middle. but overall the cake still seemed light.

I put it in the fridge so I could assemble today and when I sliced into each layer to divide it, the cake was like a brick. Like zero crumb in some places. I've never seen a cake like that.

Any thoughts as to what might have caused that?

Eileen Gray

Saturday 12th of September 2020

I couldn't say for sure. Perhaps the cake was under baked?

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