Bring some water to the boil in kettle or in a small saucepan over high heat. Once it is boiling set aside.
In a medium sized mixing bowl add the butter, powdered sugar, cocoa powder and salt.
Pour over the hot water and use a whisk to combine the ingredients together until whipped and smooth.
Add more water if needed for a thinner consistency.
Preheat the oven to 350°F
Sift all purpose flour into a mixing bowl and add light brown sugar, baking soda, cinnamon, salt and instant espresso powder.
Mix together.
Add milk, vanilla extract, oil and apple cider vinegar. Mix into a batter. Don't over-mix.
Divide between the two prepared 8-inch cake pans and smooth down.
Bake for 30 minutes for small pan or 45 min for large as I have.
Let the cakes cool in the pans for a few minutes before transferring them to a wire cooling rack to cool completely.
When the cakes are completely cool, add frosting.