A delicately flavored sponge cake with fragrant coffee buttercream frosting.
Preheat your oven to 180°C/350°F (160°C/325°F if using a fan or convection oven). Grease or line two 7-inch round cake tins.
Mix the soy milk and vinegar and set side for a few minutes. This will act as vegan buttermilk.
Mix the coffee granules with 1 tablespoon of boiling water and leave it to cool.
In a separate, large bowl, mix together the flour, baking soda and sugar.
Now add in the buttermilk and the cooled coffee, along with the vegetable oil and vanilla. Mix well until you have a smooth and creamy batter.
Divide the cake batter between the two tins and use the back of a spoon to make sure it's evenly distributed.
Bake for 15-18 minutes, until a toothpick or knife through the centre comes out clean.
Leave the cakes in the tins for 10 minutes, then flip them out onto a cooling rack and let them cool completely.
Mix the coffee granules with 1 teaspoon of boiling water and set it aside to cool. If you want your coffee cake to taste a bit stronger, just increase the amount to taste.
In a large bowl, mix together the vegan butter and icing sugar. I recommend mixing with a wooden spoon until it comes together, then whisking with an electric whisk for a minute or two to make it fluffy.
Add in your cooled coffee and gently stir it in.*
Place your first cooled cake onto a plate, board or cake stand. Using a palette knife or spatula, spread a thick later of buttercream frosting over the top.
Add your second cake on top and spread another thick layer of frosting on top of that. You can use any leftover frosting to pipe buttercream swirls around the top if you wish.
Allow the cake to sit for 1 hour so the frosting becomes firm. Then cut into slices and enjoy!