Preheat your oven to 350 degrees F. Grease and line a 9x13-inch rectangular cake pan with parchment paper.

In a the bowl of a stand-up mixer, with the paddle attachment (or in a large bowl, using an electric hand mixer), add the flour, sugar, powder, instant espresso, baking soda, baking powder and salt. Mix, on low speed, until combined.

Crack in the eggs, pour in the buttermilk, water, olive oil and vanilla extract. Mix until smooth. The batter will be thin—that’s ok!

Pour the cake batter into the prepared cake pan and bake for about 25 to 35 minutes, until a skewer inserted into the center comes out clean. Allow to cool in the cake pan for about 5 minutes and then invert onto a cooling rack and cool until room temperature before frosting.

In the bowl of a stand-up mixer, with the paddle attachment, add the butter and powdered sugar; beat until smooth and fluffy, about a minutes. Pour in the chocolate, sour cream and vanilla extract. Beat again until smooth, about 1 minute.

Scoop the frosting onto the top of the cake and make a bunch of swoops, decorating the top how you like. Sprinkle with a handful of sprinkles.

Cut and serve. If you want nice, neat slice, transfer to the fridge to chill for about 15 minutes and then slice and serve.

This cake can be wrapped with plastic wrap and kept for up to 4 days at room temperature or in the fridge.