Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a large bowl, whisk together flour, sugar, cocoa powder, baking soda, baking powder, and salt.

In a separate medium bowl, whisk together eggs, buttermilk, oil, and vanilla extract.

Add the wet ingredients to the dry ingredients and mix until just combined. Gradually add the hot water and mix until the batter is smooth and thin.

Pour the batter evenly into the prepared cake pans.

Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean.

Let the cakes cool in the pans for 10 minutes before inverting them onto a wire rack to cool completely.

In a large bowl, beat the softened butter and cream cheese together until smooth and creamy.

Gradually add the powdered sugar, alternating with the milk, and beat until the frosting is light and fluffy. Stir in the vanilla extract.

Once the cake layers are completely cool, place one layer on a serving plate. Spread a generous amount of frosting over the top.

Place the second cake layer on top and frost the entire cake, including the sides.

Decorate as desired. Chill for at least 30 minutes before slicing and serving.