Preheat the oven to 350°F (175°C). Line the cupcake tin with muffin liners.
In a large mixing bowl, combine all-purpose flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt. Mix well.
Add the eggs, whole milk, vegetable oil, and vanilla extract to the dry ingredients. Using an electric mixer or whisk, beat until smooth.
Carefully stir in the boiling water until well combined (the batter will be thin).
Pour the batter into the prepared cupcake liners, filling each about two-thirds full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted in the center comes out clean.
Remove from the oven and allow the cupcakes to cool in the tray for 5 minutes, then transfer them to a cooling rack to cool completely.
While the cupcakes are cooling, prepare the buttercream frosting. Once cooled, generously frost each cupcake.
To create the bunny face: Place a halved marshmallow on top of the frosting for ears. Use a small chocolate candy for the bunny’s nose and pipe on eyes with decorating gel.
If desired, sprinkle shredded coconut around the base of the bunny to resemble grass.