Preheat the oven to 350°F (180°C) and line a cupcake tray with 12 cupcake liners.
Sift all purpose flour and cocoa powder into a mixing bowl and add sugar, baking soda, baking powder, salt and instant espresso powder. Mix together.
Prepare the homemade buttermilk by adding ½ tablespoon of lemon juice to a measuring jug and then adding room temperature milk up to the ½ cup (120ml) line. Let it sit for a minute to curdle.
Add buttermilk, oil, egg, orange extract and orange zest to the mixing bowl and mix it into a batter.
Now add hot water and whisk it in until you have a thin batter. Don't overmix.
Divide the batter evenly between 12 cupcake liners.
Bake for 20 minutes or until a toothpick inserted into the center of one of the cupcakes comes out clean.
Let the cupcakes cool for a few minutes before removing them from the cupcake tray and transferring to a wire cooling rack to cool completely before frosting.
Prepare your frosting by adding softened butter to the bowl of your stand mixer. Start at slow speed, gradually increasing speed and beat the butter until it is smooth and slightly pale in color.
Add powdered sugar, cocoa powder, orange extract and milk and starting at slow speed gradually increase speed and let it beat for a few minutes until it's very fluffy and smooth.
When your cupcakes have cooled completely, pipe on the frosting and decorate with chocolate shavings (optional).