Place a wire rack on a tray lined with baking paper (see video above!).
Break the chocolate up into a microwave-safe jug, and melt in the microwave in 30-second bursts.*
Dip the Oreos into the chocolate one by one, touching lightly on the side of the jug afterwards to allow any excess chocolate to drip off. Place them onto the wire rack, then immediately add your decorations.
Allow the chocolate to set, then store in an air-tight container.
Video
Notes
Melting the chocolate
I usually put in the microwave for 3 x 30-second bursts. This melts most of the chocolate, and then you stir it vigorously until the rest melts (this is also a quick way to temper the chocolate).If you don’t have a microwave, just melt the chocolate on the stovetop in a smallish bowl over simmering hot water in a saucepan (make sure the bowl doesn’t touch the water).
Waiting for the chocolate to set
The chocolate on the underside of the cookies will probably stick to the wire rack a little as it dries. Don't worry about this - just lift them loose with a fork when the chocolate is nearly (but not quite) set. If you forget (like I did), it's no big deal - they'll still come loose pretty easily with a fork.
Nutrition info
Please note that the nutrition info does not include your decorations, for obvious reasons!