Add the hot coffee and mix until the batter is smooth and has no lumps of flour.
Pour the batter into the prepared baking pan and bake the cake in a 180c (350f) preheated oven for about 40-45 minutes or until a toothpick inserted into the cake comes out clean with a few moist crumbs.
Allow the cake to cool completely before frosting so the frosting won't melt off the cake.
Make the cinnamon buttercream frosting
Into a large bowl add room temperature butter, vanilla extract, cinnamon, heavy cream, and kosher salt, and mix with a hand mixer or a stand mixer until it is light and fluffy.
Then add ½ of the powdered sugar at a time (you don’t want to be in a powdered sugar cloud) and mix until smooth and silky.
Top the chilled chocolate cake with the frosting, make swirls using an offset spatula, and sprinkle chocolate shavings on top. Serve and enjoy!
Notes
Use room temperature ingredients. It is important that you use room-temperature ingredients like eggs and buttermilk. 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.
Make sure that you are using fresh ingredients like baking soda and baking powder. If they are expired your cake will not rise up beautifully.
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 the back of a knife.
Don’t overmix the batter, you don’t want to develop the gluten in the flour. This step ensures you have a moist cake and not a dense and dry cake.
Serve at room temperature for optimal taste. Bring the chocolate cake to room temperature before serving to ensure that the frosting is creamy and not hard and will melt in your mouth.
An hour or two before making the buttercream frosting, take the butter out of the fridge and let it come to room temperature. The butter should be soft to the touch. If your butter is too cold, it will be harder to mix and there will be lumps of butter in the frosting.
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.
Be patient! I know it’s extremely tempting to frost this cake as it is pulled out of the oven, but let the cake cool for at least 1 hour so it will be firmer and won’t crumble up, and prevent the frosting from melting.