Preheat the oven to 350°F (175°C) and grease mini muffin pans.

In a large mixing bowl, blend together the Devil's Food cake mix, large eggs, canola oil, and optional black food coloring until smooth.

Scoop half a tablespoon of dough into each greased mini muffin cup, pressing lightly to flatten.

Bake for 8-10 minutes until edges are set but center is still soft. Remove from oven.

While warm, create indentations in the center using a small round object.

In a clean bowl, beat the softened butter until creamy. Gradually add powdered sugar, then vanilla, salt, milk, and green food coloring until smooth.

Once cookies are cooled, fill each with green buttercream using a piping bag.

Decorate with sprinkles and candy eyeballs, and add a pretzel stick as a stirrer.

Arrange on a platter and serve to guests.