Preheat the oven to 350°F (175°C). Grease and flour the cake pans.
In a large mixing bowl, combine the flour, sugar, cocoa powder, baking powder, baking soda, and salt. Mix well.
Add in the milk, vegetable oil, eggs, and vanilla extract. Beat with an electric mixer on medium speed for about 2 minutes, until well combined.
Carefully stir in the boiling water. The batter will be thin.
Divide the batter evenly between the two prepared cake pans.
Bake in the preheated oven for 30 minutes or until a toothpick inserted into the center comes out clean.
Remove the cakes from the oven, let them cool in the pans for about 10 minutes, then transfer them to a cooling rack to cool completely.
While the cakes are cooling, prepare the buttercream frosting. In a mixing bowl, beat the softened butter until creamy. Gradually add the powdered sugar and beat until well combined. Add the milk and vanilla and mix until smooth and fluffy. Adjust with more milk or sugar for desired consistency.
Once the cakes are fully cooled, place one layer on a serving platter. Spread a layer of frosting on top, then place the second layer on top.
Frost the top and sides of the cake with the remaining buttercream frosting.
Create the bunny face by using shredded coconut to cover the top of the cake for fur. Use chocolate chips or M&M's for the eyes and a marshmallow for the nose. You can also cut marshmallows in half and place them at the top for bunny ears if desired.
Serve immediately or refrigerate until ready to serve.