Heat the oven to 350°F (175°C). Grease two 8-inch round cake pans, line the bottoms with parchment, and lightly dust the sides with cocoa powder.

Stir the plant milk and apple cider vinegar together in a measuring jug, then let the mixture stand for 5 minutes. This creates a light dairy-free buttermilk that adds tenderness and helps the baking soda work.

Whisk the flour, sugar, cocoa powder, baking soda, baking powder, and salt in a large bowl until evenly combined and no cocoa lumps remain.

Whisk the prepared plant milk mixture with the eggs, oil, and vanilla. Pour the wet mixture into the dry ingredients and stir just until the flour is absorbed.

Slowly add the hot coffee or hot water while whisking gently. The batter will be thin, which is exactly what gives the finished cake its moist texture.

Divide the batter evenly between the prepared pans. Bake for 26 to 30 minutes, or until the centers spring back lightly and a toothpick inserted in the middle comes out with a few moist crumbs.

Cool the cakes in their pans for 10 minutes, then turn them onto wire racks and remove the parchment. Let the layers cool completely before frosting.

For the frosting, place the chopped dairy-free chocolate in a heatproof bowl. Warm the coconut milk until steaming but not boiling, pour it over the chocolate, and let it stand for 3 minutes.

Whisk the coconut milk and chocolate until smooth, then stir in the vanilla. Chill for 30 to 45 minutes, stirring occasionally, until thick enough to spread; add powdered sugar if you prefer a sweeter, firmer frosting.

Place one cake layer on a serving plate, spread with frosting, and top with the second layer. Cover the top and sides with the remaining frosting, then garnish with chocolate curls or a light cocoa dusting.