Mise en place. Place parchment paper on a cookie sheet. Use shortening if needed to help the parchment paper stick to the sheet.
Melt 3/4 of semi-sweet chocolate for 30 seconds at 50% power. Stir (even if nothing is melted yet). Heat for addition 15 second cycles at 50% power, stirring well between each interval. Once chocolate is melted, add rest of semi-sweet chocolate. Stir until everything is melted.
Pour out and spread into a thin layer on parchment paper-lined cookie sheet.
Melt 3/4 of mint chips for 30 seconds at 50% power. Stir (even if nothing is melted yet). Heat for addition 15 second cycles at 50% power, stirring well between each interval. Once mint is melted, add rest of mint chips. Stir until everything is melted.
Drizzle on top of semi-sweet chocolate. Use a knife to make swirls.
Sprinkle chopped Oreos across top of mint chocolate. Press down slightly to make them stick well.
Allow everything to cool completely. Break up into chunks.
Notes
***If semi-sweet chocolate hardens too much while mint chips are melting, place in oven on lowest possible setting possible for 15-30 seconds, until chocolate softens.
***If you absolutely must, you can substitute white chocolate (or green candy melts) and mint extract for the mint chips. Results are quite as still good, but are pretty good.