Preheat the oven to 350°F (175°C). Grease two 9-inch round cake pans, then line the bottoms with parchment paper and lightly grease the paper for easy cake removal.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt until everything is evenly blended and free of lumps.

Crack in the eggs, then pour in the whole milk, vegetable oil, and vanilla extract. Beat the mixture on medium speed until a smooth batter forms.

Slowly pour the hot brewed coffee or hot water into the batter while mixing on low speed. Continue stirring until fully incorporated. The batter will be thin, which helps produce a moist cake.

Divide the batter evenly between the prepared cake pans. Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean or with only a few moist crumbs attached.

Allow the cakes to cool in their pans for about 10 minutes. Carefully remove them from the pans and transfer to a wire rack. Let the layers cool completely before adding frosting.

Beat the softened butter until creamy. Gradually mix in the powdered sugar and cocoa powder. Add the heavy cream, vanilla extract, and a pinch of salt. Continue beating until the frosting becomes smooth, fluffy, and easy to spread.

Place one cake layer on a serving plate and spread a generous layer of chocolate frosting over the top. Add the second cake layer and cover the top and sides evenly with the remaining frosting. Let the cake rest for about 20 minutes before slicing and serving for the best texture.