Preheat your oven to 350°F (175°C) and grease three 12-count mini muffin pans thoroughly.

In a large bowl, combine the Devil's Food Cake Mix, large eggs, canola or vegetable oil, and black food coloring. Stir until smooth.

Scoop about ½ tablespoon of batter into each greased muffin cavity and flatten each scoop with a spoon.

Bake for 8-10 minutes, remove when edges are set, and create an indentation in each cookie.

Allow the cookie cups to cool in the pans for 5 minutes, then transfer to a wire rack to cool completely.

Beat the softened unsalted butter until creamy, then gradually add the powdered sugar, vanilla extract, and salt.

Mix in milk, one tablespoon at a time, until you achieve a pipeable consistency, then add green food coloring.

Fill each indentation in the cookie cups with the green buttercream using a piping bag.

Decorate with green sprinkles, Halloween sprinkles, candy eyeballs, and pretzel sticks.

Serve immediately or store in an airtight container for 3-4 days.