Line a baking sheet with parchment paper or wax paper. Lay your cookies side-by-side on the baking sheet.
Put the white chocolate melts in a microwavable bowl or mug and microwave for 30 seconds. Stir well and then microwave for 10 seconds at a time, stirring in between each, until the chocolate is fully melted.
Use a spoon to put the melted chocolate into a sandwich baggie. Snip a little bit off of one corner to make a hole. You can use a piping bag with a small tip on it if you prefer.
Pick up one of the cookies and squeeze the chocolate over the top arc of the cookie. Do your best to keep the chocolate on the front of the cookie and keep the back side clean. Gently tape the bottom of the cookie against a flat surface to make the melted candy begin to ooze down the cookie. Shift it from side-to-side to create uneven edges on the bottom of the ghost.
Place the cookie back on the parchment paper with the back side against the paper and the decorated front facing up. Continue until all of your cookies have been decorated with the white chocolate.
Let the white chocolate fully harden, approximately 10 minutes.
Next place the chocolate chips in a microwave mug or bowl and melt it just like you did with the white chocolate.
Use a spoon to put the melted chocolate into a sandwich baggie. Snip a little bit off of one corner to make a hole. You can use a piping bag with a small tip on it if you prefer.
Pipe three circles on each ghost cookie, 2 eyes and a mouth.
Let the chocolate harden completely then store in an airtight container until ready to serve.