Preheat the oven to 350°F (175°C)
Grease and line two 8-inch cake pans
Mix flour, cocoa powder, sugar, baking powder, baking soda, and salt in a bowl
Add eggs, milk, oil, and vanilla extract
Stir in hot water or hot coffee until smooth
Divide the batter evenly between the pans
Bake for 30 to 35 minutes
Cool the cakes in the pans for 10 minutes
Remove the cakes from the pans and cool completely
Melt chocolate with butter or cream for the frosting
Beat in powdered sugar and a little milk or cream until smooth
Place one cake layer on a plate
Spread frosting over the top
Add the second cake layer
Frost the top and sides of the cake
Chill briefly before serving