Lemon Mousse Cake

Earlier this month saw David, our dear friend and neighbour, celebrate his 81st birthday.  Being a firm believer that birthday celebrations are never complete without a cake I donned my pinny and got into the kitchen to bake.

Knowing that David has a fondness for lemon flavours and light cakes in particular I searched through my extensive collection of baking books and came across a recipe for a version of a lemon chiffon cake, in 'Cakes & Cake Decorating'.  The image for the cake showed it presented simply with no fuss.  It really did look delicious with a thick layer of lemon mousse sandwiched within a straightforward swiss roll type of sponge.  However, as I read the method it became clear that the recipe was far from suitable for our elderly neighbour due to the raw eggs within the mousse layer.  The mousse also contained gelatin which, living in a vegetarian household, is a product which I clearly don't use.  The cake obviously needed modifying to suit the specific needs of David and of course ourselves.

Our, or rather David's,  Lemon Mousse Cake was made with a genoise sponge. The butter added to a genoise cake not only brings a little extra moisture and flavour to the sponge but also prevents it from spoiling as fast as a swiss roll type of bake.  The light lemon mousse filling was adapted from the vegetarian egg free mousse I used in our Triple Chocolate and Mango Tart.  A generous amount of homemade lemon curd was incorporated into a lightly whipped double cream.  Beaten aquafaba was then added in place of raw eggs.  The cake also contained a layer of the homemde lemon curd bringing an extra lemony flavour to the affair.

Although aquafaba was discovered in the vegan world it definitely has worthwhile benefits for the elderly, like David, and also for those who are very young, pregnant or living with a compromised immune system.  For those who haven't come across this wonder, aquafaba is the often disposed of liquid which surrounds tinned beans (not baked beans!)  Believe it or not, it can be used in the same way as we use egg whites!  It makes great meringues, macarons, mousses, pasta... the list is endless!  Although any bean liquid can be used, chickpea water does seem to be the preferred choice.   I must admit that it does take a little longer to whip up than the conventional egg white, and for that reason I would definitely suggest using electric beaters rather than a balloon whisk which would certainly give your arms a workout.  Once the aquafaba has been whisked with the icing sugar (and white wine vinegar to stabilise) and then combined with other flavours, such as the lemon curd and double cream like in this lemon mousse, any strange flavour detected in the aquafaba's liquid form is certainly no longer noticeable.

The birthday boy, David, was delighted to have received a cake to celebrate his big day and, like us, thoroughly enjoyed the clear lemon flavours housed within the light and airy genoise sponge.

So, let's get to it and bake!

Lemon Mousse Cake     Yum

Yield: 1 x 20cm cake

Serves: 10
Difficulty: Moderate
Time: hands on time about 35 minutes (longer if making your own curd); plus 20-25 minutes bake time; cooling time.
Freezable: Yes, undecorated
Inspired by:  'Lemon Chiffon Cake' in the book Cakes and Cake Decorating

You will need:

20cm Springform Cake Tin
Greaseproof Paper
Large Glass Mixing Bowl
2 x Medium Mixing Bowls
Pan
Electric Hand Held Beaters
Tea Towel
Sieve
Spatula or large metal Spoon
Balloon Whisk
Serrated Bread Knife
Piping Bag
Plain Round Nozzle (I used number 12)

For the sponge mixture

4 medium eggs
65g Golden Caster Sugar
60g Caster Sugar
125g Plain Flour (I used gluten free) + 1 tsp for greasing
32g Unsalted Butter + extra for greasing

For the Lemon Mousse & finishing the cake

50ml aquafaba liquid (ideally from a can of unsalted chickpeas)
50 Icing Sugar
½ tsp White Wine Vinegar
approx ¾ jar Lemon Curd (either shop bought or homemade lemon curd)
300ml Double Cream

How to make it:

1.  Pre-heat the oven to 200c / Fan 180c / Gas 6.

2.  Prepare the cake tin.
Grease the inside of the cake tin thoroughly and line the base with
greaseproof paper.  Place the teaspoon of flour into the greased cake
tin and, holding it on its side and over the sink, tap the cake tin so
that the flour adheres to the greased sides of the tin.  Knock out any
excess flour.

3. Weigh the cake ingredients.
Have all of your cake ingredients ready as you need to work swiftly once
the batter has been beaten to help reduce the loss of volume.  Sieve
the flour 3 times.  Fold a tea towl into quarters and place on the work
surface.

4.  Melt the butter.  Place the butter
into a small pan and set over a low heat to slowly melt.  Remove from
the heat once it has melted and set aside.

5.  Make the sponge.
Add some water to the pan so that it is no more than a quarter
full.  Break the eggs into a large glass bowl and suspend this bowl over the
pan.  Ensure the water in the pan doesn't touch the bowl.   Place the
pan over a low heat on the hob.  Using the electric beaters (or balloon
whisk if you're feeling energetic) lightly whisk the eggs.  Add the two
sugars and continue beating on a medium setting for about 7 minutes.  The egg mixture will initially be frothy, but will gradually
become thicker the longer the mixture is beaten.  You're aiming for
ribbon stage.  This is where the mixture leaves a trail on the surface
when the beaters are lifted.  You should be able to write the number 8
without the ribbon sinking into the mixture until the number has been
completed.

6.  Fold in the flour and butter.
Remove the bowl from the pan and sit it on the tea towel.  Pour the
butter down the side of the bowl into the mixture so that it's not
landing directly onto the top of the aerated batter.  Sieve the flour
into the mixture.  Using a spatula or large metal spoon start to gently
fold the flour and butter into the mixture.  Ensure you get to the
bottom of the bowl where flour can become trapped.  Avoid over working
the mixture.  The batter will deflate a little during this process, but
do aim to work gently yet speedily.

7.  Fill the cake tin.  Pour the batter into the prepared cake tin from a low height.

8.  Bake.
Place the cake tin in the centre of the oven and bake for about 20
minutes.  It will be baked when the cake is golden brown and slightly shrinking away from the sides.  Remove from the oven and place on a cooling tray.
After a couple of minutes, unclip the cake tin and gently remove from the cake.  Use a fish slice (or similar) to gently remove the sponge from the base of the cake tin.  Allow the cake to to fully cool on the cooling rack.

9.  Start making the lemon mousse.   Place the
measured liquid from the chickpeas into a bowl and beat with the
electric beaters until firm.  Add the icing sugar a teaspoonful at a
time, beating well after each addition.  Add the white wine vinegar and
beat for a further minute.  The meringue should be thick and glossy now.
Set aside.

9.  Continue making the lemon mousse.  Pour the double cream into another bowl and beat with a balloon whisk to
soft peaks, avoid over beating.   Add 10 tsp lemon curd (see note a) and mix gently to combine.  Don't worry if the cream has become a little thick at this stage as the aquafaba will slacken it a little.  Add one third of the aquafaba meringue and
mix together to slacken the mixture.  Add the remaining aquafaba and gently fold together with a spatula until combined.  Taste and add a little more lemon curd if required.

10.  Begin to assemble the lemon mousse cake.
Once the cake is fully cold place it onto the board / stand you want to
serve it on.   Use a serrated bread knife to cut the cake in half
horizontally.   Carefully set the top half aside.  Spread a little lemon curd onto the cut surface of the cake and spread out almost
to the edge with a pallet knife or back of a spoon (see note a).

11.  Complete assembling the lemon mousse cake.  Spoon the lemon mousse filling into a piping bag fitted with a plain round nozzle.  Pipe 'blobs' of the mouse onto the lemon curd layer, aiming to keep the blobs fairly close together and as neat as possible along the exposed edge.  Place the top half of the cake onto the filled base, ideally in the same
orientation that it was removed.  Starting in the centre of the cake
pipe blobs of the lemon mousse to the top surface, aiming to keep them all roughly the same size.  Continue until the whole of the top
of the cake is covered.  Place 2 tsp lemon curd into a small bowl.  Add two of drops of water to slacken and stir, you're aiming for a fairly runny consistency.  Use a teaspoon to drizzle the runny lemon curd over the top of the cake.

Enjoy!

Notes:

a)  Some shop bought lemon curds can be particularly thick, if this is the case spoon the curd into a small bowl and add half a teaspoon of water and stir to combine.  You're aiming for a nice spreadable consistency which won't pull at the cake crumb when spread. Add a little more water if necessary.
b) Consider finishing the cake with some crystallised lemon zest.