• Preheat the oven to 180°C (350°F). Line three or two 8-inch (20 cm) round cake pans with parchment paper.

Make the cake:

• Combine the instant coffee with the boiling water and stir until the coffee has completely dissolved. Set aside to cool to warm or room temperature. To make it cool faster, you can mix the coffee with some of the milk from the recipe.
• Add all the dry ingredients to a large mixing bowl and whisk until the mixture is well combined. Add all the wet ingredients including the coffee mixture and mix until just combined. The batter should be runny. Divide the batter evenly between your cake pans.
• If you're baking 3 x 8" cakes, bake them for 20-23 minutes. If you're baking 2 x 8" cakes, bake them for 30-35 minutes. The cakes are ready when you insert a toothpick in their center and it comes out clean (a few moist crumbs are fine).
• Let the cakes cool in their pans for 20 minutes, then transfer them to a cooling rack. Cool completely.

Make the frosting:

• Combine the coffee with the milk or cream, stirring until the coffee has completely dissolved.
• Add the butter to a large bowl or stand mixer and beat until it's pale and fluffy. Add the sugar, coffee, vanilla and salt and beat on low speed until just combined. Increase the speed to high and beat until the frosting is light and fluffy. Taste test the frosting and add more sugar for a sweeter or firmer frosting. If you want more coffee flavor, dissolve the coffee in a little liquid again and beat it into the frosting. Chill the frosting until needed.

Make the espresso caramel (optional, prepare this at least 2 hours before decorating):

• Combine the coffee with half of the cream, and stir until the coffee has completely dissolved. Set aside.
• In a small saucepan, mix the sugar and the remaining half of the cream. Place over medium heat and cook until the sugar has melted and the mixture turns golden brown. Watch the caramel as it will burn quickly.
• Add the coffee mixture and stir for around 30 seconds to combine. Add the butter and whisk until the caramel is smooth. Cook the caramel for at least 5 minutes to thicken. Cook it for longer if you prefer a thicker caramel, keeping in mind that it will thicken when it cools (note 3 for troubleshooting). Set aside in the fridge or freezer or until the caramel has completely cooled.

Decorating the vegan espresso cake:

• If your cakes have domes on top, use a large serrated knife to slice off the domes and to create a flat surface. Place one cake layer on a serving plate, spread around ½-¾ cup of frosting on top and layer another cake on top. Repeat for the second and third layers. Finally, use an offset spatula to cover the entire cake with the remaining frosting. If desired, swirl the espresso caramel on top of the cake.
• Store the cake at room temperature in an airtight container until serving. If it's a hot day, keep the cake in the refrigerator and let it come to room temperature before serving.
• Store leftover cake slices in a container at room temperature for 2 days, in the fridge for up to 4 days or in the freezer for up to 1 month. Allow the cake to come to room temperature before serving.