**For the Cake:**

1. Preheat your oven to 350°F and prepare a 9″ cake pan by lining it with parchment paper and greasing it with butter or oil.
2. If making your own buttermilk, mix ½ cup milk with ½ tablespoon vinegar, stir, and set aside.
3. In a large bowl, mix together the flour, sugar, baking powder, baking soda, and salt. Make sure to sift the ingredients to remove any lumps.
4. Add the egg, vegetable oil, and buttermilk to the dry ingredients. Use a whisk to gently mix until just combined.
5. In a separate bowl, mix the boiling water with cocoa powder and instant coffee until smooth and shiny.
6. Add the cocoa mixture to the cake batter and gently fold until fully combined.
7. Pour the batter into the prepared cake pan and smooth the top with a spatula.
8. Bake in the preheated oven for 20-25 minutes, or until a toothpick inserted into the center comes out with moist crumbs attached.
9. Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.

**For the Ganache:**

1. Heat the cream in a small saucepan until it just begins to boil.
2. Pour the hot cream over the chopped chocolate and let it sit for 5 minutes.
3. Stir the mixture until smooth and glossy.
4. Let the ganache sit for another 5 minutes to thicken slightly.
5. Pour the ganache over the cooled cake and spread it evenly with a spatula.
6. Slice, serve, and enjoy your decadent chocolate creation!