Preheat the oven to 350°F.
Grease the bottom and sides of a round 9-inch cake pan, then dust them with cocoa powder. Line the bottom with parchment paper, grease the parchment paper, then dust it with cocoa powder (Note 1).
Whisk the flour, cocoa powder, sugar, baking powder, baking soda, cinnamon, and salt together in a large mixing bowl.
In a small container such as a liquid measuring cup, stir together the milk, olive oil, apple cider vinegar, vanilla, and espresso powder.
Pour the milk mixture into the bowl with the flour mixture, then stir to combine. Make sure the dry ingredients are fully saturated and the batter is mostly smooth, but don't overmix — a few lumps are fine.
Pour the batter into the prepared baking pan.
Bake the cake for 25 to 28 minutes, until a toothpick inserted into the center comes out mostly clean with just a few moist crumbs.
Place the cake on a cooling rack and let it cool completely.
While the cake cools, make the topping. Place the chocolate chips into a medium bowl.
Heat the coconut milk either in the microwave or in a saucepan on the stove until it just barely comes to a simmer, then pour it over the chocolate chips. Let the mixture sit for 5 minutes.
Stir the mixture until the chips melt completely (Note 2). Stir in the vegan butter until it melts into the mixture.
Once the cake has cooled, run a knife along the edges to loosen it, then invert the cake onto a plate (Note 3). Remove the parchment paper and spread the topping over the cake, taking it to the very edge so a bit drips down the sides, if you'd like.
Allow the ganache to set, optionally placing the cake in the fridge (recommended).
Slice and serve.