Blueberry Lemon Mousse Cake

blueberrylemon6I’m officially in my third week of the summer holidays (perks of working at a college!) and it’s gotten to the point where now, I’m bored. I mean, everyone else I know is either still working, or already off on holiday. And whilst I am set to be heading down to Cornwall next week for a mini break, right now I’m stuck at home undecided on what to do on a daily basis.

Today however, I was sitting at home thinking about cake. Happens. So I decided to bake.

Though, in this ridiculous heat that London has been blessed/cursed with right now I didn’t fancy being stuck in front of a hot oven all day.

But cake.


So I made mousse cake. Minimal baking and a light, chilled dessert with fresh fruit flavours. Perfect in the heat!

I’d made a mousse with marshmallows before which was super easy and tasty so I opted for that. It does get a bit messy, but cake.

blueberrylemon5For the sponge I separated the eggs. In the bowl with the yolks I added half the sugar and whisked until pale yellow and fluffy. In another bowl I whisked the egg whites and cream of tartar till it formed soft peaks, then finally whisked in the remaining half of sugar till glossy.

IMG_5786I then folded in the flour and melted butter.

IMG_5789 IMG_5792I baked this at 200°C for approximately 15 minutes. You don’t want it to rise at all as you’ll need a flat top. The surface browned a little and did start to rise slightly, but it quickly deflated once out of the oven.

IMG_5799For the lemon mousse I melted the white chocolate in one bowl, melted the marshmallows in another (large!), and whisked the double cream and lemon zest to stiff peaks in a third. I then combined the three with the lemon juice and mixed with a electric whisk to try to break down any lumps.

IMG_5812 IMG_5815 IMG_5825 IMG_5832I then poured this over the cake layer and left ing to chill in the fridge for 2 hours.

IMG_5835For the blueberry mouse I again melted the marshmallows in a large bowl, and whisked the double cream to soft peaks in another. I then blitzed the blueberries and sugar together in a mini blender, and added this to the cream. Then combined with the melted marshmallows and mixed with an electric whisk to remove any lumps.

IMG_5840 IMG_5843 IMG_5845 IMG_5847Before I poured this on top of the lemon mousse layer I made sure it had come down to room temperature, but not too much that it was starting to re-solidify.

blueberrylemon1I left this to chill overnight before serving, but a minimum of 6 hours shooooould do the trick if you can’t wait that long ;).


Blueberry Lemon Mousse Cake
Recipe Type: Dessert
Author: Acorns & Custard
  • For the sponge:
  • 3 eggs
  • pinch of cream tartar
  • 90g caster sugar
  • 90g plain flour
  • 45g unsalted butter, melted
  • For the lemon mousse:
  • 200g white chocolate
  • 125g mini marshmallows
  • 275ml double cream
  • juice and zest of 2 lemons
  • For the blueberry mousse:
  • 200g blueberries
  • 25g caster sugar
  • 180g mini marshmallows
  • 200ml double cream
For the sponge:
  1. Preheat oven at 200°C.
  2. Separate the eggs.
  3. With the whites, whisk with the cream of tartar until you have soft peaks.
  4. Add half of the sugar and whisk again until glossy.
  5. In another bowl, beat the egg yolks with the other half of the sugar.
  6. Fold the egg whites into the yolk mixture.
  7. Add the flour and melted butter and fold in, trying to keep as much air in as possible.
  8. Pour into the bottom of a lined baking tin (mine was a diameter of 22cm).
  9. Bake for 15 minutes until slightly golden on top. It may start to rise but it will deflate once out of the oven. Also, if it comes away from the sides that’s ok, the mousse will fill the gaps.
  10. Leave to cool.
For the lemon mousse:
  1. Melt the chocolate over a saucepan of simmering water, or heat at 30 second intervals in a microwave (taking care not to let it burn!!).
  2. Place the mini marshmallows in a large heatproof bowl and microwave till they puff up. Stir until the marshmallows have evenly melted and have lost their shape. You could also melt them in a saucepan over a very low heat if you’d prefer. You will be left with a gooey, sticky mess (it’s better than it sounds, promise!). Stir in the lemon juice and white chocolate (you may want to use an electric whisk to remove any lumps).
  3. Whisk the double cream to form soft peaks, and stir in the lemon zest.
  4. Fold the whipped cream into the marshmallow mixture, then pour over the sponge base.
  5. Leave to cool for AT LEAST 2 hours.
For the blueberry mousse:
  1. As before, melt the marshmallows (in a large heatproof bowl in the microwave, or in a saucepan over a very low heat).
  2. In a blender, blitz up the blueberries and the sugar to a pulp, the smoother the better!.
  3. Whisk the double cream to form soft peaks, then stir in the blueberry mixture so the colour is even throughout.
  4. Fold the whipped blueberry cream into the marshmallow mixture (using an electric whisk to remove any lumps), and leave to cool to room temperature before pouring through a sieve on top of the lemon mousse.
  5. Leave this to cool completely, preferably overnight but to a minimum of 6 hours.


9 thoughts on “Blueberry Lemon Mousse Cake

    1. I’ve not tried it with frozen… it should be fine when mixing into the whipped cream. Though, when it comes to stirring in the melted marshmallow i’d be worried the cool temperature would cause it to start setting. Maybe best to thaw them beforehand?

      1. Can you translate the measurements to US standard measurements? I want this recipe to succeed. For instance, 200g of white chocolate equates to 7.05 ounces, and each ingredient is treated the same with an odd US measurement. Also when you say to cool the mousse cake, should it go in the refrigerator during the 6 hours, or sit outside of the frig?

      2. Sorry for the delayed response!!!

        For the sponge:
        3 eggs
        pinch of cream tartar
        3oz caster sugar
        3oz plain flour
        1.5oz unsalted butter, melted
        For the lemon mousse:
        7oz white chocolate
        4oz mini marshmallows
        10oz double cream
        juice and zest of 2 lemons
        For the blueberry mousse:
        7oz blueberries
        10z caster sugar
        6oz mini marshmallows
        7 fl oz double cream

        I think those measurements are close enough! Also, yes you do chill it in the fridge… should have mentioned that! Hope that helps! Do let us know how it goes! 🙂 xxx

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