Preheat the oven to 350°F (175°C). Grease and flour your baking pan(s). In a large bowl, sift together the all purpose flour, cocoa powder, granulated sugar, baking soda, baking powder, and salt.

In a separate bowl, whisk together the milk, eggs, vegetable oil, and vanilla extract (if using). Slowly add the wet ingredients into the dry ingredients, mixing until smooth.

Carefully stir in the boiling water the batter will be thin, but this helps make the cake moist. Fold in the shredded coconut. Pour the batter into the prepared pan(s). Bake for 25 to 30 minutes or until a toothpick inserted into the center comes out clean. Remove from oven and allow to cool completely on a wire rack.

Using an electric mixer, beat softened butter until creamy. Gradually add powdered sugar, alternating with heavy cream, until you reach desired consistency. Add vanilla extract and green food coloring, mix well until evenly colored.

If needed, slice and shape the cake layers into segments to resemble a caterpillar body. Frost the cake generously with green buttercream. Use assorted candies or chocolate chips to create the eyes, mouth, and other caterpillar features.