• Pre-heat oven to 180°C / 160°C fan assisted oven / gas mark 4 and line and grease 2 x 8 inch round cake tins.
• Melt the chocolate in a bain marie, or a glass bowl set over a pan of boiling water, then set aside.
• Pour the milk into a jug and stir in the apple cider vinegar. Let stand for 5-10 minutes to curdle slightly.
• In a large mixing bowl, or stand mixer, whisk together the flours and starches, cocoa powder, espresso powder, bicarbonate of soda and salt until well mixed.
• In a separate bowl mix together the vinegar milk, sugars, olive oil, eggs and vanilla then beat into the flour mixture.
• Finally mix in the melted chocolate until completely incorporated.
• Divide the mixture between the 2 cake tins and bake in the oven for 35 minutes or until an inserted skewer is removed without a wet crumb.
• Turn out the cakes and cool on wire racks before filling with buttercream.

Chocolate Fudge Buttercream

• Melt the chocolate in a bain marie or a glass bowl set over a pan of boiling water, then set aside to cool.
• Beat butter together with the icing sugar in a stand mixer for at least 6 minutes until light and creamy, scraping down the sides every so often.
• Add the cocoa powder, melted chocolate and salt then beat until smooth and incredibly creamy.