Start by making the ganache; place the chopped chocolate in a heat-proof bowl. Heat the coconut milk until it is just boiling then pour it over the chocolate.
Set aside for 2 minutes then stir until smooth and the chocolate is completely melted. Cover and place in the fridge for about 2 hours, stirring occasionally, while you make the cake.
Preheat the oven to 180C/350F/gas mark 4. Grease three 15cm/6inch round tins and line the bases with baking parchment (or use two 20cm/8inch tins instead).
Whisk together the almond/soy milk and vinegar in a large jug; the milk should curdle slightly. Whisk in the sugar, oil and vanilla extract.
In a large bowl, sift together the flour, cocoa powder, baking powder, bicarbonate of soda and salt.
Gradually whisk the wet ingredients into the dry until smooth; be careful not to over-mix. Divide the batter evenly between the tins and bake for about 30 minutes, until a skewer inserted into the centre comes out clean.
Leave the cakes to cool in their tins for 30 minutes then carefully turn them out onto a wire rack to cool completely (they are delicate so be gentle). If you are making them a day in advance, wrap in clingfilm once cool.
To assemble the cake, place one of the layers on a serving plate/cake stand. The ganache should be thick but spreadable, if it is too runny still then return it to the fridge until it is firm, or pop it in the freezer for a bit to speed up the process. If it is too thick then gently warm it over a pan of hot water until it has softened.
Spread a third of the ganche over the first cake layer and place another cake on top, spread over another third of the ganache and repeat. Decorate as you see fit - with fresh berries, vegan chocolates, candied nuts etc.
Store in an airtight container at room temperature unless it is very warm, in which case keep the cake in the fridge; allow to come up to room temperature to serve.