Who says vegan desserts can't be decadent? The bottom layer of this two-tier chocolate cake is covered with mocha icing, while the top is blanketed with ganache.
Cake: Preheat oven to 375 degrees. Lightly brush two 8-inch round cake pans with oil; set aside.
Sift flour, cocoa, baking soda, salt, and granulated sugar into a large bowl. In a small bowl, dissolve espresso powder in 2 cups warm water; whisk in oil and vanilla. Whisk wet ingredients into dry mixture until well incorporated. Quickly whisk in vinegar. Divide batter between prepared pans. Bake until a tester inserted into centers comes out clean, about 35 minutes. Let cool 10 minutes, then invert cakes onto a wire rack and let cool completely.
Icing: in the bowl of a mixer fitted with the paddle attachment, beat margarine on medium speed until light and creamy, about 2 minutes. Add confectioners' sugar, espresso powder, soy creamer, and vanilla; beat until smooth, 30 seconds more. Beat in cooled chocolate; set aside.
Trim tops of cakes flat. Place a cake layer on a cake plate. Spread 1 1/2 cups icing evenly over it (reserve remaining icing for another use). Top with second cake layer, cut-side down.
Ganache: Place chocolate in a medium heatproof bowl. Bring golden syrup and soy creamer to a boil in a small saucepan over medium-high heat. Remove from heat and pour over chocolate. Let stand 2 minutes, then stir until smooth. Pour ganache over cake, allowing it to drip down sides. Let stand at room temperature until set, at least 15 minutes.
Remaining icing can be stored in an airtight container in the freezer for up to 3 months.
Coconut milk or coconut creamer can be substituted for the soy creamer.