Preheat the oven to 350°F (175°C). Grease a 10-inch Bundt pan (minimum 6-cup/1.5 L capacity) thoroughly with cooking spray or vegan margarine.
Melt the dark chocolate using a heatproof bowl over simmering water or in short bursts in the microwave. Set aside.
In a medium bowl, whisk together the flour, brown sugar, cocoa powder, baking powder, baking soda, and salt.
Add the oat milk, oil, and vanilla extract to the dry ingredients and whisk until smooth.
Stir in the hot coffee and melted chocolate until fully combined, then gently fold in the chocolate chips.
Pour the batter into the prepared Bundt pan and smooth the top.
Bake for 35 to 40 minutes, or until a skewer inserted into the center comes out clean.
Cool in the pan for 10 minutes, then carefully invert onto a wire rack. If needed, briefly dip the outside of the pan in hot water to help release the cake.
To make the icing, heat the coconut cream and vanilla until hot but not boiling. Remove from the heat and whisk in the cocoa powder until smooth, then whisk in the powdered sugar and salt until thick and glossy.
Pour the icing over the completely cooled cake immediately before it begins to firm up. Let the icing set before slicing and serving.