Preheat oven to 350°F/180°. Grease an 8x8-inch square pan or 9-inch round pan. Set aside.

To make the cake: In a large bowl, mix together the flour, baking powder, salt, and cocoa powder. In a separate bowl, whisk together the coconut milk, vegetable oil, sugar, vanilla, vinegar, and baking soda. Add the wet ingredients to the dry ingredients and mix until just combined.

Scrape batter into prepared pan. Bake cake for 25-30 minutes until a skewer inserted into the center comes out clean. Avoid overbaking which will make the cake dry. Allow cake to cool completely on a wire rack in the pan.

To make the vegan ganache: Place chocolate and coconut milk in a medium heat-proof bowl, and microwave in 20-30 second-intervals, stirring in between each interval, until melted. Alternatively, set the bowl over a saucepan of simmering water, stirring occasionally, until melted.

Allow the ganache to cool slightly and pour over completely cooled cake. Refrigerate until set.

Cake can be kept in the refrigerator in an airtight container for up to 5 days. Serve at room temperature for the best texture.