Preheat oven to 350°F (175°C).
Grease two 9-inch round cake pans and line with parchment paper.
In a large bowl, sift flour, cocoa powder, sugar, baking powder, baking soda, and salt. Whisk to combine.
In another bowl, mix milk, oil, eggs, and vanilla until smooth.
Gradually add wet ingredients to dry ingredients, mixing on low speed (or by hand) until just combined.
Slowly pour in hot water/coffee and stir until the batter is thin but uniform.
Divide batter evenly between pans.
Bake for 30–35 minutes or until a toothpick inserted comes out clean.
Let cakes cool in pans for 10 minutes, then transfer to a wire rack.
Frost with chocolate ganache or buttercream once completely cooled.
