Lay a sheet of parchment paper across your counter or on a baking tray. Set out your Oreo cookies in a row so they're ready to dip as soon as the chocolate is melted.
Add the chocolate chips to a microwave-safe bowl and heat in 30-second bursts, stirring in between each round. Keep going until the mixture turns fully smooth and glossy, which usually takes about a minute total.
Dip one side of each Oreo into the melted chocolate, letting any extra drip back into the bowl. Place the cookie chocolate-side up on your parchment paper right away.
While the chocolate is still wet, press an unwrapped Hershey's Kiss into the center of each cookie. Sprinkle your Halloween sprinkles around the rim so they stick to the melted chocolate before it firms up.
Move your tray to the fridge for about 10 to 15 minutes so the chocolate hardens completely. Once set, your witch hats are ready to serve or pack away for later.