Preheat your oven to 170°C (325°F). Prepare three 18 cm (7 in) cake tins with cooking spray or butter and line with baking paper.
Place the flour, sugar, cocoa and baking soda in the bowl of a stand mixer fitted with the paddle attachment, and mix on low to combine. Add the butter and mix on low until the mixture resembles breadcrumbs. (You could do this by hand—see the vanilla cake recipe on page 61—but really, the stand mixer is the way to go.)
In a separate bowl, dissolve the instant coffee in the warm water (or just use the shot of espresso), add the eggs, oil and vanilla and mix together. Add two-thirds of the wet mixture to the dry ingredients and mix on medium-high until thick and fluffy. Add the remaining wet ingredients and mix well until combined and the batter is smooth. Make sure you scrape down the bowl and then continue mixing, as the dry mixture can get stuck at the bottom and you really want a nice, smooth consistency.
Add the buttermilk and mix slowly to combine. There may be small chunks of buttermilk but don’t fret, this is normal. This batter is also wetter than the basic vanilla recipe, so don’t panic if it’s not thick.
Pour the mixture evenly into the prepared tins (use your scales to get them all the same; see my tips on page 25), and bake for 30–40 mins until a skewer or knitting needle poked into the cakes comes out clean. Allow to cool in the tins for 5–10 mins, then turn out onto cooling racks.
When the cakes are cool, wrap them in plastic wrap and chill for 2 hours or overnight—this will make them easier to trim and ice (see my instructional on this, pages 68–79).
This cake goes perfectly with EVERY type of icing. If you are after something classic, go for Dark Chocolate Ganache (page 115); if you want to balance the rich chocolate cake with something lighter, use Vanilla Bean Swiss Meringue Buttercream (page 107).
You can also add coconut or frozen fruit to this cake to change up the chocolatey flavour profile. See our flavour inspos below for . . . well, inspo of course.