Into a large mixing bowl, add the flour, baking powder, espresso powder, kosher salt, and granulated sugar, sift the cocoa powder, and mix with a whisk until combined.
Add the eggs, vegetable oil, buttermilk, and vanilla extract, and mix until almost combined.
Add the hot water and mix until just combined and there are no lumps of flour visible! Do not overmix.
Pour the cake batter into an 8-inch cake pan. Smooth it out with a spatula and bake in a 180c (350f) preheated oven for 40-45 minutes or until a toothpick inserted into the cake comes out with a few moist crumbs.
Make the chocolate ganache
Melt dark chocolate and heavy cream in a small to medium mixing bowl in the microwave for about 50 seconds.
Let the chocolate and the cream sit for 10 minutes for the chocolate to melt, then mix until the chocolate ganache is smooth and silky.
Place the chocolate ganache in the fridge for about 40 minutes or until it hardens and has a frosting-like texture.
Frost the cake with the chocolate ganache and smooth it out with a spatula. Serve and enjoy!
Notes
Use room temperature ingredients. It is important that you use room-temperature ingredients like eggs and milk. This step ensures that your mixture mixes into a homogenous mixture and bakes perfectly. you don’t want to place cold batter into the oven.
Don’t overmix the batter, you don’t want to develop the gluten in the flour. This step ensures you have moist cake and not dense and dry cake.
Measure your flour correctly! When measuring your flour, avoid scooping it with a measuring cup. Instead, stir the flour with a spoon to create as many air pockets as possible, and spoon it into your measuring cup. Finally, level it with a back of a knife.
Be patient! I know it’s extremely tempting to eat and frost this cake as it's pulled out of the oven, but let the cake cool for at least an hour so it will be firmer and won’t crumble up. This step ensures that the frosting won’t melt off the cake. You never want to frost warm cupcakes or cakes.
Line your baking pan with parchment paper! This step helps the cake to bake evenly, and it makes sure that your cake will release easily from the pan.