01 -
Preheat oven to 350°F (177°C). Lightly grease three 12-cup mini muffin pans.
02 -
In a large bowl, mix cake mix, eggs, oil, and black food coloring if using until thoroughly combined.
03 -
Scoop approximately 1/2 tablespoon of dough into each mini muffin cup. Flatten the dough with your fingers to prevent doming. Bake for 8 to 10 minutes until edges are set.
04 -
Immediately after baking, press a 1-tablespoon measuring spoon into the center of each warm cookie to create an indentation. Let cool completely in the pans before transferring to a wire rack.
05 -
Beat softened butter in a large bowl until creamy. Gradually add powdered sugar, vanilla, and salt. Beat until smooth. Add milk one tablespoon at a time until a piping consistency is achieved. Mix in green food coloring until desired shade is reached.
06 -
Once cookie cups are cooled, pipe green buttercream into each cavity, filling to resemble bubbling potion.
07 -
Top each filled cookie cup with round green sprinkles, Halloween sprinkles, candy eyeballs, and insert a half pretzel stick to mimic a stirring rod.
08 -
Serve immediately or store cookie cups in an airtight container at room temperature for 3 to 4 days, or refrigerate up to 1 week. Freeze undecorated cookie cups for up to 3 months.