Line a cookie sheet with a silicone baking mat and set it aside.
Carefully separate the Oreos. You want all of the filling on one side of the cookie
Melt the dark chocolate wafers in a microwave-safe bowl till smooth. Melt in the microwave in 30-second intervals, stirring to prevent burning. Or melt according to the package instructions.
Spoon about 1 teaspoon of the melted chocolate onto the center of the Oreo filling. Press a popsicle stick into the chocolate, then spoon about half a teaspoon more of chocolate on top of the stick.
Place the other half of the cookie on top and press together gently. It's okay if some chocolate oozes out of the sides! You can gently smooth it around with the back of a teaspoon.
Repeat the steps with the remaining cookies, and set them aside for the chocolate to harden. You can place them in the refrigerator to speed up the process.
Remelt the chocolate, if required, and stir until smooth. Carefully dip each Oreo cookie pop into the chocolate, covering it completely. Gently tap it on on the edge of the bowl to get rid of excess chocolate.
Add two black pearl sprinkle "legs" to the bottom of the chocolate-coated cookies on either side of the popsicle stick as “legs.” Place on the prepared cookie sheet to dry. Repeat for the remaining cookies and leave to set. Again you can pthem e in the fridge to speed up the process.
When the cauldrons are set, melt the green candy according to the package instructions. Transfer the melted candy to a disposable piping bag and cut off the tip.
Gently peel the chocolate cookie cauldron from the silicone baking mat. Holding it in one hand, pipe the melted green candy over the top to make it look like ooze coming out of the cauldron. Sprinkle over some green pearl sprinkles to create a 3D effect. Then add purple pearls, skulls, eyeballs, and bat sprinkles to complete the potion! Set aside to harden. (See notes)