Preheat the oven to 180°C (160°C fan) or Gas Mark 4.
Lightly grease a 20 cm round cake tin.
Stir the lemon juice into the oat milk and set aside to curdle slightly, creating a vegan buttermilk.
In a saucepan over medium heat, melt the margarine with the syrup and coffee granules (if using).
Stir well and let cool slightly.
Sift the flour, cocoa powder, sugar, baking powder, and bicarbonate of soda into a large mixing bowl.
Whisk to combine.
Pour the oat milk mixture and melted margarine mixture over the dry ingredients.
Stir well until a smooth batter forms.
Pour the batter into the prepared cake tin and bake for 30-35 minutes, or until a skewer inserted into the center comes out clean.
Let the cake cool in the tin for 10 minutes, then turn it out onto a wire rack to cool completely.
To make the frosting, beat all frosting ingredients together until smooth.
Once the cake is completely cool, spread the frosting evenly over the top.
Notes & Wine Advice
Serving Tip:For extra indulgence, top with fresh berries or a sprinkle of cocoa powder.Wine Advice:Pair with a sweet dessert wine like Port or a fruity red such as Zinfandel.