White Chocolate Mud Cake with Pistachio and Rosewater

Recently I realised that the majority of the layer cakes on my blog are 6” rounds. Because of their smaller size, I find they can be quicker to bake and decorate, but still nice a tall, leaving with you with more than enough cake to feed a small crowd. That said, sometimes bigger is better and totally necessary, especially if you’re planning a big celebration, so I decided to up the anti and share my white chocolate mud cake recipe which I’ve been working on for a while...

White chocolate can get a bit overlooked, especially when up against milk and dark. I’ve shared many chocolate cake variations on my blog, and dark chocolate fudge cake is one of the most popular flavour choices when I make custom cakes for friends and family. Whilst super sweet white chocolate might not be quite as sophisticated in comparison, I still really love it - probably because it reminds me bingeing on white chocolate buttons as a child!

The pistachio paste might seem like it'll take a lot of effort to make, but believe me - once you combine it with the buttercream for the filling, it'll be totally worth it. In fact, it's just topped my ultimate cake filling list (shortly followed by lemon curd)!

Although I think rose water rounds this recipe off perfectly, I left the buttercream flavour open ended. I love the floral aroma of rose water, but appreciate that it’s not everyone’s cup of team (my boyfriend included). If you’re not a fan, coconut works really well here, and if you’re STILL not a fan, then vanilla is a fail-safe winner for sure.

Oh, and how could I not finish the cake with some floral buttercream swirls?! For this technique I used a JEM 1M nozzle - piping the swirls by starting inwards and working outwards. You can practice on some baking paper before piping onto the cake, but once you get the hang of it, it's really simple (and quite therapeutic!). 

What you need (for a 8" layer cake):

For the white chocolate mud cake:
600g white chocolate
450g unsalted butter
475g caster sugar
450ml milk
6 medium eggs
3tsp vanilla
350g plain flour
350g self raising flour
2tsp baking powder

For the pistachio filling:
100g pistachios
2tbsp maple syrup
2tbsp vegetable oil
4tbsp of the buttercream (pre flavouring and colouring)

For the rosewater buttercream:
8 medium egg whites (approx. 250g)
500g caster sugar
500g unsalted butter (cubed and brought to room temperature)
2tsp rosewater (optional - substitute with a vanilla or coconut extract if preferred)
1 drop of pink gel food colouring
A handful of pistachios roughly chopped (for decoration)

What you need to do:

For the white chocolate mud cake:

1. Place the chocolate, butter, caster sugar and milk into a large saucepan and set over a medium heat. Stir occasionally until all of the ingredients have melted, the pour into a large mixing bowl and set aside to cool slightly
2. While the mixture is cooling, preheat your oven to 160°C and then grease and line four 8” round cake tins with baking paper - if you don’t have four tins, you can bake the sponges in two tins and then cut into four layers once cooled, but you will need to adjust the baking time to suit
3. Once the mixture has cooled (the bowl will still be slightly warm but not hot), crack the eggs into a small bowl and whisk briefly
4. Add the vanilla into the mixture, then slowly fold in the flour and baking powder
5. Divide the mixture into your baking pans to bake for around 40-45 minutes (checking the sponges after around 30 minutes)
6. Once baked, remove from the oven and leave to cool in the tins

For the pistachio filling:

1. Preheat your oven to 180°C and place the pistachios on a baking tray - roast the nuts for 10 minutes, until they're starting to brown
2. Once the nuts are ready, place them in a food processor and blitz for around 8 minutes until you have a ground pistachio powder
3. Pour the maple syrup and vegetable oil into the food processor and continue to mix until you get a paste - this can take up to 15 minutes
4. Once you've made your buttercream (see instructions below), spoon four tablespoons of the (unflavoured and uncoloured) buttercream into the paste and stir to combine, then chill until you're ready to fill the cake

For the rosewater buttercream:

1. Whilst the cakes are cooling, prepare your buttercream... Place your egg whites and sugars into the bowl of a freestanding mixer Place the bowl over a bain-marie and whisk the mixture by hand until the sugar has dissolved and has reached 72°C on a thermometer (approximately 10 minutes)
2. Remove the bowl from the saucepan and wipe the bottom of the bowl dry with a tea towel, then place back onto your mixer and whisk on medium speed until you have a thick meringue - the bottom of the bowl should still feel warm to the touch
3. Gradually add the butter, increasing the speed, then continue to whisk until you have a soft, silky buttercream - this can take up to 15 minutes
4. Once the buttercream is ready add four tablespoons of buttercream to your pistachio paste, then finally add the rosewater (or vanilla or coconut extract) to the remaining buttercream and mix in a small srop of pink gel food colouring (I use Sugarflair) and transfer into a bowl for decorating...

To assemble and finish:

1. If your sponges are domed, trim the top of each layer so you have flat, even layers of sponge
2. Place around four tablespoons of your pink buttercream in a piping bag and cut a medium sized hole in the bag. Place the bottom layer on a cake board or plate, then pipe a buttercream 'forte' around the edge of the sponge, then fill the center with one tablespoon of the pistachio filling - repeat with two more layers, stacking them on top of each other as you go then add the top layer and press down slightly to secure
3. Coat the cake with a thin layer of buttercream (this is your crumb coat) then leave to chill in the fridge for around 30 minutes
4. Once the crumb coat has chilled, remove the cake from the fridge and coat with a second layer of buttercream, smoothing all of the sides and edges - for the semi-naked effect you should end up with some of the sponge peeking through at this point, with enough leftover buttercream to complete the rosettes on top
5. To decorate the top, take a large star nozzle and place it in a large piping bag with the remaining buttercream and slowly pipe buttercream swirls on top of the cake. To create the rosettes, start piping on the inside, then slowly move around in a circular motion towards the outside, creating a snail-like swirl
6. Finally, finish the cake with a sprinkling of chopped pistachios, then slice and enjoy!