1233. Courgette Chocolate Cake with Mulberry Swiss Buttercream

Using my mulberry bounty in an altogether new and innovative way, this recipe is a chocolate cake frosted in mulberry Swiss buttercream. It's no ordinary chocolate cake either; this is the ultra-moist courgette chocolate cake, which may count towards your five a day.
Of course, you may substitute almost any berry for the mulberries. Blackberry would probably be most suitable, but then again so would blueberries and raspberries.

Ingredients:

Chocolate Courgette Cake:
2 1/2 cups flour
1/2 cup cocoa
2 tsp baking soda
1/2 tsp salt
2 eggs
2 cups sugar
1 cup light olive oil
1/2 cup buttermilk
2 tsp vanilla
1/2 cup boiling water
2 cups grated courgette

Mulberry Swiss Meringue Buttercream:
2/3 cup egg whites (from about 4 eggs)
1 1/4 cups sugar
1 1/2 cups butter, cut into cubes or slices
Pinch of salt
1/2 tsp vanilla
1/2 cup mulberry puree at room temperature, seeds removed through a sieve.

Method:

Chocolate Courgette Cake:
Preheat oven to 350F.  Grease and flour two 9-inch spring form cake pans. Set aside.
In a large bowl sift together flour, cocoa, baking soda and salt.  Set aside.
In the bowl of a stand up mixer beat eggs,  With the mixer running, slowly add sugar and mix until light yellow in color. Slowly add olive oil, buttermilk and vanilla.  Mix until smooth and light in color.  Beat in flour and cocoa mixture until smooth.  Beat in grated courgette then boiling water.  Pour batter into prepared baking tins and place in preheated oven.  Bake for 35 minutes or until cake springs back when lightly touched.  Remove from oven and cool for 5 minutes.  Invert cakes onto a cooling rack until completely cool.

Blackberry Swiss Meringue Buttercream:
In a very clean bowl of an electric mixer, add egg whites and sugar.  Place over a simmering pot of water, stirring constantly until temperature reaches 160F.  Rub a small amount of the mixture between two fingers to make sure the sugar is dissolved.  Remove from heat.
Using the whisk attachment, beat until the mixture is a thick meringue and the bottom of the bowl is cool to the touch. The bowl must be cool before adding the butter.
Replace the whisk with the paddle attachment.  With the mixture on medium-low speed add butter once slice at a time until all of the butter has been incorporated.  The mixture should be silky smooth and thick.  The mixture may begin to look curdled, keep mixing until it is smooth.  This can take 10 minutes or so.  Mix in salt and vanilla.  Add mulberry puree, if using.  Once the puree is added keep mixing until mixture is silky again.

To assemble:
Slice each cake in half horizontally to get a total of four layers. Frost each layer with the buttercream then frost the entire surface and sides of the cake with the buttercream. Best served at room temperature.

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