Place the chocolate discs in a microwave safe bowl and melt in bursts of 20 seconds, stirring between each burst. Alternately, melt the chocolate in a heat proof bowl set over a saucepan filled with 1 inch of water, bring to a boil and stir the chocolate often. Stir in a few drops of the peppermint oil to taste. It will be strong so start with a light hand.
Pour the popcorn and cashews into a large bowl (do in batches if necessary.) Pour the melted chocolate over the popcorn and cashews and stir to combine. Pour out in a single layer on a baking sheet lined with parchment paper and let it dry completely.
While popcorn mixture is drying, melt the red and green chocolate using your preferred method.
Once the popcorn is completely dry, use a fork to scoop a bit of the red chocolate and drizzle it over the popcorn n streaks. Let the chocolate dry and then repeat with the green chocolate. Allow chocolate to dry between colors.
Once all the layers are dry, use a clean spatula to carefully scrape the bottoms of the baking sheets to lift and break apart the popcorn.