Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a mixing bowl, combine flour, sugar, cocoa powder, baking powder, baking soda, and salt. Mix well.
Add eggs, milk, vegetable oil, warm water or coffee, and vanilla extract. Mix until smooth.
Pour the batter evenly into the prepared pans. Bake for 30 minutes or until a toothpick comes out clean.
While the cake cools, prepare the ganache by heating the cream until just boiling, then pour it over the chopped chocolate. Let it sit for a few minutes, then stir until smooth.
If using, add butter to the ganache for extra shine and mix well.
Once the cakes are completely cool, frost with the chocolate ganache.
Notes
For a richer flavor, use coffee instead of warm water.