Easy 3 Ingredient Lemon Mousse (Cake Filling or Topping)

Now that I've shared my Mom's Old Fashioned Sour Cream Pound Cake Recipe, I can share the magnificent lemon mousse topping that was born to top that cake. This magical 3 Ingredient Lemon Mousse was first created as a complex orange cream topping with made-from-scratch orange curd mixed with homemade whipping cream. Dreamy, right?

But who wants to make citrus curd from scratch every time you need a creamy cake filling or topping? So for this recipe, we're grabbing a jar of store bought lemon curd, whipping some heavy cream and adding a little gelatin. Y'all. It's magic. The mousse stays light and creamy but the gelatin firms it up just enough to hold its shape inside a cake or as a topper. And the lemon curd brings all the sweet and silky citrus to the party.

This lemon mousse is delightful in three applications.

Cake Filling:

As you can see in the picture above, I used it in a Portuguese sponge cake (called Pao do Lo) traditionally made in a springform pan. Cooled it and sliced it in half and filled the cake layer with the lemon mousse then topped it with berries and sugared candied lemon zest.

The mousse held up beautifully inside the cake for about 36 hours. It may have lasted even longer...if only the cake around it had not been eaten so quickly. Be sure to chill the mousse cake for 90 minutes before cutting to serve.

Cake Topper:

I don't want to bias the jury, but this lemony airy mousse is the perfect topper for Mom's Old Fashioned Sour Cream Pound Cake. A spoonful of the mousse on top of cake with berries, especially if you've buttered and grilled the cake slices, is the perfect dessert for any special occasion dinner party, brunch or afternoon tea.

Straight Outta The Bowl:

Exhibit A

Here's what you need to make 3 Ingredient Lemon Mousse:

• Lemon curd
• Cold heavy whipping cream
• Unflavored gelatin + 1 tablespoon water

Step by step instructions for easy lemon mousse:

1. Make gelatin mixture.

Begin by chilling a large bowl and the beaters for the electric mixer. If using a kitchen aid, chill the bowl of an electric mixer and your whisk attachment. Ensure your heavy cream is well chilled.

Add one tablespoon of water to a microwave safe cup and sprinkle gelatin over the top of the water. Set aside for 3-4 minutes until the gelatin water thickens.

Microwave the gelatin mixture until the gelatin fully dissolves, about 5-8 seconds. Stir gelatin mixture and set aside to cool. I like to add 1 tablespoon of the heavy cream to the warm gelatin mixture to cool it.

2. Form whipped cream.

In the chilled large mixing bowl, add the cold heavy cream and whip on medium-high speed until soft peaks form. Slowly stream in the cooled gelatin mixture as you continue mixing the whipped cream until stiff peaks form.

Add the lemon curd to the whipped cream mixture and whip at low speed just until fully incorporated. Use a rubber spatula to scrape the bottom of the bowl. Taste to ensure lemon flavor is balanced and at the ideal level for your lemon desserts.

3. Combine with cake.

The fluffy lemon mousse is now ready for its final destination. If using as a cake filling, use a pastry bag to pipe filling between cake layers and add any remaining mousse to the top of the cake with fresh berries and lemon slices or sugared lemon peel. Use an offset spatula to smooth the sides of cake for a rustic, even finish. Chill the lemon mousse cake on the serving plate for 90 minutes before cutting and serving.

If using as a cake topper, cover the mousse with plastic wrap and refrigerate until serving. As we discussed earlier, grilled pound cake is the perfect vehicle for for lemon mousse.

If eating straight out of the bowl, grab a spoon and go to town.

FAQ's about 3 Ingredient Lemon Mousse Cake Filling and Topping:

Can I use orange curd?

You can! I've also made homemade strawberry curd for this recipe. All of it is delicious. Start with the recommended ratio of heavy cream to curd, taste and adjust for a stronger fruit flavor.

How much lemon mousse would I need for a 3 layer cake?

The recipe as written yields about 2 - 2 ½ cups of lemon mousse. If you are making a two-layer cake that needs a good portion of lemon mousse on top of the cake, I recommend using 1 ½ cups of heavy cream, ½ cup of lemon curd and 1 ½ teaspoons gelatin. For a three-layer cake, I recommend doubling the recipe (2 cups of heavy cream, ⅔ cup lemon curd and 2 teaspoons gelatin) to have enough mousse for all three layers.

To store, wrap the mousse tightly with plastic wrap or transfer to airtight container and keep in refrigerator up to 3 days.

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