Prepare the Cake:

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

In a large mixing bowl, sift together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.

Add the eggs, milk, oil, and vanilla extract to the dry ingredients. Beat on medium speed until well combined.

Gradually stir in the boiling water until the batter is smooth. Note: The batter will be thin.

Pour the batter evenly into the prepared pans.

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

Remove from the oven and allow the cakes to cool in the pans for 10 minutes. Then, transfer them to a wire rack to cool completely.

Prepare the Frosting:

In a large bowl, beat the softened butter until creamy.

Sift together the powdered sugar and cocoa powder. Gradually add this mixture to the butter, alternating with the heavy cream, beating on low speed until combined.

Add the vanilla extract and increase the mixer speed to medium-high. Beat until the frosting is light and fluffy.

Assemble and Decorate:

Place one cake layer on a serving plate. Spread a layer of frosting on top.

Place the second cake layer on top and frost the top and sides of the cake.

Decorate with Halloween-themed candies and sprinkles as desired.