BERRY BALSAMIC FILLING

1. Place all the ingredients in a small saucepan. Place over medium heat, and cook, stirring often, until the mixture comes to a boil. Cook for a further 5-6 minutes, then strain the mixture, reserving the fruit, and returning the liquid to the pan.
2. Cook the liquid, stirring constantly, for 2-3 minutes or until reduced slightly. Return the reserved fruit to the pan and mix well to combine. Transfer to a container, cover, and place in the fridge to chill completely.

SMALL BATCH CHOCOLATE LAYER CAKE 

1. Preheat the oven to 325°f / 160°c. Grease and line two 6" cake pans with parchment paper circles. 
2. In a medium bowl, whisk together the flour, sugar, salt, baking powder, and baking soda. In a separate medium bowl, whisk together the eggs, milk, oil, and vanilla.
3. Add the wet ingredients to the dry ingredients and mix to incorporate. 
4. Boil the water and place the cocoa and espresso powder in a medium bowl (I use the same one I just used for the wet ingredients). Weigh the water directly into the bowl, then mix to combine until it forms a paste. Ensure that there are no lumps. 
5. Add the cocoa powder paste to the bowl with the cake batter in, and whisk well to combine. 
6. Divide the cake batter between the two pans using your scale (approximately 420g per pan). Get rid of any big bubbles by banging the pan on the counter top. 
7. Bake the cakes for 35 to 40 minutes, or until a tester inserted into the centre comes out clean or the middle bounces back when lightly pressed. 
8. Remove the cakes from the oven and leave to cool in their pans for 10 minutes then transfer to a cooling rack and remove the parchment paper and leave on the rack to cool completely. 

CHOCOLATE SWISS MERINGUE BUTTERCREAM 

1. Place the egg whites, sugar and salt in the bowl of a stand mixer or a heat proof bowl. Place over a pot of simmering water, ensuring that the water does not touch the bowl. Heat, whisking constantly, until the mixture registers 160˚f / 70˚c on a thermometer and the sugar has dissolved.
2. Carefully transfer the bowl to the mixer, and fit with the whisk attachment. Whip the egg whites on high until they are snowy white and fluffy, 8-10 minutes. Add the butter one chunk at a time. The mixture may look curdled - but just keep mixing! Once all the butter is incorporated, mix on high for a further 10 minutes. Add the vanilla and mix until incorporated.
3. While the buttercream is mixing, melt the chocolate in a small heatproof bowl in 30 second increments in the microwave. Set aside to cool slightly.
4. Once the buttercream has finished mixing, and is smooth and silky, add in the cooled chocolate, and sift in the cocoa. Mix for a further 2-3 minutes, then switch to the paddle attachment and mix on low for one minute to remove any air. 

ASSEMBLY 

1. Level off the cakes if desired.
2. Transfer some of the buttercream to a piping bag fitted with a medium round tip or just with the end snipped off - this will be used to make a buttercream dam to hold in the berry filling between layers.
3. Secure one of the layers of cake to a cake turntable or serving platter using a little buttercream. Add about half a cup of buttercream onto the first layer of cake, and smooth using an offset spatula.
4. Create a buttercream dam using the buttercream in the piping bag by piping a ring of frosting around the outside edge of the first layer. Fill in the ring with the berry balsamic filling (leave any extra juicy stuff behind, you may not need all of it).
5. Place the second layer of cake onto the first, upside down to give you a flat top edge, pressing very lightly to secure, and sealing the joins with a layer of buttercream. At this point I like to pop the cake into the freezer just for 10 minutes to ensure the buttercream dam will hold strong.
6. Crumb coat the cake - to do this, apply a thin layer of buttercream over the entire surface of the cake (top and sides), and smooth with a bench scraper or icing smoother. You can chill the cake now if you like, or you can continue on frosting it. I like to chill it if I am giving it a smooth finish, but found I do not need to if it is a rustic one like this.
7. Apply a second, slightly thicker layer of buttercream over the entire surface of the cake (top and sides), and smooth off briefly with an offset spatula and scraper. Using your offset spatula, create swoops in the frosting. Smooth off the top edge. Alternatively, finish as desired.
8. Store in the fridge until serving. Allow to stand at room temperature for 20-30 minutes before serving. Store leftovers in the fridge (see note in blog post about how I like to keep layers fresh).