I’m partnering with Oregon Berries to make this absolutely delicious blackberry mousse cake!

It’s made with tender blackberry swirled cake layers, the fluffiest blackberry mousse filling, and blackberry buttercream frosting.

It’s truly bursting with Oregon blackberries and tastes just like sunshine!

I love using fresh blackberries when they’re in season, but to be totally honest I use frozen berries the rest of the year.

Oregon blackberries are naturally ripened, picked at peak ripeness and flash frozen within 24 hours of being picked. This locks in all their delicious flavor and means that frozen berries are just as wonderful to bake with as fresh berries.

As an added bonus, frozen berries have a longer shelf life and are actually a better value compared to fresh berries. It’s truly a win-win situation!

How to Make This Blackberry Mousse Cake

To make sure your blackberry mousse layer cake turns out as amazing as possible, let’s walk through each step together!

I’ve also included a video tutorial of the process below.

Step 1: Make the Blackberry Mousse

Make the blackberry mousse first so it has time to chill. It can also be made 1-2 days ahead of time.

Melt the white chocolate by placing it in a medium-sized, heat-proof bowl with heavy cream.

Microwave for 45-60 seconds, then let the mixture sit for a minute and stir until combined using a rubber spatula. This can also be done in a double boiler.

Then stir blackberry jam into the white chocolate mixture. If desired, add a small squirt of purple gel food coloring to give this mousse a more vibrant purple color.

Mix thoroughly until the mixture is smooth and there are no clumps of jam. Set aside.

Next, add the heavy cream, powdered sugar, vanilla extract, and a pinch of fine salt into a large bowl or the bowl of a stand mixer fit with a whisk attachment.

Mix on medium-high speed until the whipped cream starts to gather in the whisk attachment and you can see texture around the edges of the bowl (see photo below).

At this stage, the whipped cream should be thick and able to keep its shape.

This usually takes about one to two minutes in my stand mixer.

Gently fold the whipped cream into the blackberry white chocolate mixture in two additions.

Use a rubber spatula to swoop around the sides of the bowl and pull through the center.

Be careful not to over-mix the mousse, or it will become deflated and lose its structure.

Cover the mousse with plastic wrap and chill in the refrigerator for at least 2 hours.

Make sure you keep the mousse chilled until right before you fill the cake because it can also lose its shape if it gets warm.

Step 2: Bake and Level the Blackberry Swirled Cake Layers

Next, make the blackberry swirl and vanilla cake batter following the recipe card at the bottom of this post.

Pour half of the batter evenly between the prepared cake pans. I added about 275g of batter per pan.

Drizzle 1/2 cup of blackberry jam over the cake batter. I put my jam in a piping bag to make it easier to drizzle, but you can also use a spoon.

Use a small offset spatula or butter knife to swirl the blackberry jam into the cake batter.

Top with the remaining batter, adding another 275g of batter to each pan.

Smooth the batter with a spatula or small offset spatula so that it’s even across the pan.

Bake for 32-35 minutes or until a toothpick comes out with a few moist crumbs.

Remove the cake layers from the oven and let them cool in the pans for about 10 minutes.

Gently run an offset spatula around the rim of the cake pans to loosen them, then flip them into wire racks to finish cooling.

Once the cake layers have cooled to room temperature, use a serrated knife to level the top of each cake layer.

It makes the cake so much easier to stack and assemble!!

If you’re making these in advance, you can wrap and freeze them at this point.

Step 3: Make the Blackberry Buttercream

While the cake layers bake and cool, make the blackberry American buttercream.

I like to use American buttercream because I think it’s the easiest to make and I love eating it. However, it is quite sweet!

If you want to use a less sweet frosting, I’d recommend making a batch of my Swiss meringue buttercream or my hybrid buttercream.

This frosting can also be made in advance if needed and kept in the fridge for up to a month!

If your frosting seems too thick after mixing your ingredients, add in additional cream (1 tablespoon at a time).

Or if the frosting is too thin, add in more powdered sugar (quarter of a cup at a time).

If you’re unsure how thick your frosting should be, you can learn what consistency you’re looking for in my frosting consistency post.

Step 4: Stack and Fill the Cake Layers

Stack and frost the cake layers on a greaseproof cake board using a dab of blackberry buttercream to help stick the first cake layer to the board.

Pipe a double ring of the purple blackberry buttercream around the perimeter of each cake layer.

Spread 1/4 cup of blackberry jam inside the frosting ring, then top it with an even layer of blackberry mousse. Use about 1/2 of the mousse between each layer.

Then gently press blackberries into the mousse.

Chill the cake in the freezer for about 10 minutes, then repeat with the next cake layer. This helps lock the filling in place and prevents the layers from sliding around as you frost the cake.

Once all the cake layers are stacked, spread a thin coat of frosting around the cake to fully cover the cake layers.

If your layers are sliding around, insert a chopstick or wooden dowel into the center of the cake to make it more stable.

Smooth the frosting around the cake with a bench scraper, then chill the cake for about 10 minutes in the freezer.

This will help the filling between the cake layers firm up and make the cake way easier to frost.

Step 5: Decorate This Blackberry Mousse Cake

Add a second, thicker layer of purple blackberry frosting to the cake and smooth using a bench scraper.

Pipe swirls of the different colors of buttercream in a curved line around the side of the cake and up on top of the cake like in the pictures above.

Start with the pink buttercream and pipe large buttercream rosettes, then gently press some fresh blackberries into place.

Fill in the gaps with swirls and dollops of the other colors of buttercream, then enjoy!

Substitutions & Swaps: Blackberry Swirled Cake Layers

While I love this recipe just the way it is, I know some of you might not have all these ingredients on hand.

Below are some swaps and substitutions that can be made in this recipe:

• Cake Flour – This recipe turns out best with cake flour. If you can’t find cake flour, you can make your own makeshift cake flour using this method. You can also swap in a good gluten free flour blend (like this) if needed. Just be sure to stir the batter longer than normal to help give the cake proper structure, and let the batter sit for about 20 minutes before baking it if you opt to make a gluten free version.
• Granulated Sugar – I do not recommend reducing the amount of sugar or changing the type of sugar, as it will change the texture of the cake layers.
• Sour Cream – You can also use full fat yogurt, buttermilk, whole milk, or an alternative yogurt or milk (almond, soy, oat).
• Vegetable Oil – Use any flavorless oil in this recipe. Canola, vegetable, or even sunflower oil would all work great. I don’t recommend olive oil though, as it has a strong flavor and will change the taste of the cake.
• Egg whites – This recipe uses large egg whites. I like to use the type that come in a carton so that I don’t have to separate my eggs, but you can also use fresh egg whites. If you have an egg allergy you can try using a vegan egg replacer. You can also use 5 large, whole eggs but they will change the texture of the cake layers a bit.

Substitutions & Swaps: Blackberry Buttercream & Mousse

Some swaps and substitutions that can be made in this frosting recipe include:

• Unsalted Butter – If you only have salted butter on hand, you can use it in place of the unsalted butter. Just be sure to omit the salt that this frosting recipe calls for. You can also use vegan butter in its place!
• Heavy Cream – Coconut cream can be used in place of the heavy cream as a dairy-free alternative.
• White Chocolate – You can use white chocolate chips or good-quality white chocolate bars to make the blackberry mousse.
• Blackberry Jam – I love using my blackberry freezer jam in this recipe, but any seedless blackberry jam or jelly made with Oregon blackberries should work great!

Making This Cake in Different Sizes

I used 8″ cake pans to make this cake, but this recipe can be used to make different sized cakes. You can also half or double the ingredients to make a half or double batch!

You can make four 7″ or 6″ cake layers with one batch of batter. Bake the cake layers at 350 F / 175 C for 34-37 minutes or until a toothpick comes out with a few moist crumbs.

One batch of batter can also be used to make one 9×13-inch sheet cake. Bake it at 350 F for 40-50 minutes and use flower nails or heating cores to help the cake bake evenly.

You can also use this recipe to make a Bundt cake! Bake time can vary based on the size and type of pan you use and can take anywhere from 45-75 minutes. I recommend using a toothpick to test for doneness and checking on it every 5-10 minutes once it’s been in the oven for 45 minutes.

The final variation of this recipe is cupcakes!! This recipe makes about 36 regular sized cupcakes. Fill 3/4 full and bake for 17-19 minutes or until a toothpick comes out with a few moist crumbs.

Tips for Making the Best Blackberry Mousse Cake

• When making the blackberry mousse, chill your mixing bowl and whisk attachment in the freezer. It makes it easier and quicker to whip up the whipped cream for the mousse.
• Properly measure your flour (spoon into the cup measure, then level). Or better yet, use a kitchen scale to measure your dry ingredients.
• Mix the cake batter just until the ingredients are incorporated once you add in the flour. This will ensure your cake layers are tender and fluffy.
• Use a scale to weigh your cake pans as you fill them. It will make your cake layers bake to the same height and bake more evenly.
• Bang your cake pans on the counter before putting them in the oven. This brings any big air bubbles that are trapped in the batter to the surface.
• Level your room temperature or thawed cake layers with a serrated knife to make them easier to stack.
• Chill your cake layers in the freezer for about 20 minutes before assembling the cake. It makes it so much easier to stack and frost them!

Making This Cake in Advance and Storage Tips

Make your cake layers in advance and freeze them. It breaks the process up and makes it more approachable.

The blackberry mousse can also be made in advance! Make it up to 2 days in advance and store in the fridge.

Make the blackberry frosting ahead of time or save any leftover frosting. Store in an airtight container in the fridge for up to a month.

This frosting can also be stored in the freezer for up to 3 months! Just be sure to give it a good stir once it thaws to make it nice and smooth again. This cake can last in the fridge for up to 2 days.

Let Me Know What You Think

If you try this cake recipe, I’d love to hear what you think! Please leave a comment and rating below.

And don’t forget to tag us @chelsweets and @oregonberries so that we can see your delicious creations on social media!

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