Preheat oven to 180°C (350°F) and grease two cake pans.
In a bowl, mix flour, sugar, cocoa powder, baking powder, baking soda, and salt.
Add eggs, milk, oil, and vanilla; mix until smooth.
Stir in hot water to create a thin batter.
Divide into pans and bake for 25–30 minutes, then cool completely.
Heat cream and pour over dark chocolate; stir until smooth.
Add butter and powdered sugar, mixing into a rich fudge frosting.
Layer cakes with frosting between and on top.
Chill slightly before slicing for clean layers.
