01 - Preheat oven to 350°F (175°C). Lightly grease a 12-cup muffin pan or line with paper liners.
02 - In a large mixing bowl, cream unsalted butter with granulated sugar until pale and fluffy. Incorporate the egg and vanilla extract until fully blended.
03 - In a separate bowl, whisk together all-purpose flour, cocoa powder, baking powder, and salt. Gradually add to the butter mixture, mixing just until combined.
04 - Divide dough evenly into 12 portions. Shape each into a ball, then press into the base and up the sides of each muffin cup to form a well for filling.
05 - Bake for 13 to 15 minutes, or until set. If the centers puff, gently press down with a spoon immediately after removing from the oven. Cool completely in the pan.
06 - Melt chocolate chips in a microwave or over a double boiler until smooth. Brush or spoon melted chocolate inside each cooled cookie cup to create a cauldron interior. Allow to set until firm.
07 - Pipe or spoon colored frosting into each cup. Top generously with assorted candies to mimic bubbling potions, finishing with edible glitter if desired.
08 - For a whimsical touch, insert a curved piece of black licorice onto either side of each cup to form a handle, anchoring gently into the rim.
09 - Arrange cauldron cups on a platter and serve at room temperature.