From Cut out and keep, one of my new favourites website, here is an AMAZING (And not light at all) recipe:
You will need:
Oreos, either one or two, depending on how much do you want to indulge
Half a Marshmallow
2 rectangules from regular milk chocolate
With Two Oreos: If you're going for the double Oreo version (good decision), repeat the same steps as above, simply using a whole Oreo for the top and bottom. It may take a few more seconds in the microwave, but it's oh so worth it.