An easy chocolate sponge cake topped with creamy ganache.
Preheat your oven to 180°C/350°F (or 160°C/325°F if using a fan or convection oven). Line an 8 x 10 x 3-inch deep rectangular tray with baking paper.
Mix together the soy milk and apple cider vinegar. Set aside for 5 minutes to allow it to curdle and thicken slightly.
In a large bowl, mix together the flour, baking soda, cocoa powder and sugar until well combined.
Add the milk mixture from earlier into the bowl along with the oil and vanilla extract. Mix well until you have a smooth batter, making sure to scrape any dry mixture from the bottom of the bowl.
Add the chocolate chips and fold them in.
Transfer the cake batter to your baking tray and bake for 25-30 minutes, until a toothpick through the center comes out clean.
Fill a small saucepan with a little bit of boiling water on the stove. Place a slightly larger heat-proof bowl over the pan. Make sure the water isn't touching the bottom of the bowl (just pour a little out if it is).
Place the chopped chocolate and soy milk into the bowl and turn the heat to medium-low.
Stir gently until all of the chocolate has melted and there are no lumps left.
Turn the heat off and carefully remove the bowl from the pan. Let it cool at room temperature for around 1 hour, by which time the ganache should be slightly firmer.
Let the cake cool in the tin for 10 minutes then flip it out onto a wire rack and leave it to cool completely.
Spread the ganache over the cake and top with chocolate shavings if using.