01 - Line a baking sheet with parchment paper or a silicone baking mat.
02 - In a heatproof bowl, melt the dark chocolate over a pot of simmering water using a double boiler or in the microwave in 30-second bursts, stirring until smooth.
03 - Stir half of the peppermint extract into the melted dark chocolate until well combined.
04 - Pour the dark chocolate onto the prepared baking sheet and spread it into an even rectangle measuring approximately 8x10 inches.
05 - Melt the white chocolate in a clean bowl using the same double boiler method or microwave technique.
06 - Stir the remaining peppermint extract into the melted white chocolate until incorporated.
07 - Gently pour the white chocolate over the dark chocolate layer. Use a skewer or toothpick to swirl the two chocolates together for a marbled effect.
08 - Immediately sprinkle green candy-coated chocolates, green sprinkles, and pistachios over the top, pressing them lightly into the chocolate to adhere.
09 - Refrigerate the bark for 45 minutes, or until completely firm and set.
10 - Once set, break the bark into irregular pieces and serve immediately or store in an airtight container.