01 - Line a baking sheet with parchment paper or a silicone baking mat to prevent sticking.
02 - In a heatproof bowl, melt the dark chocolate over a pot of simmering water using a double boiler method, or microwave in 30-second bursts, stirring frequently until completely smooth.
03 - Stir half of the peppermint extract into the melted dark chocolate until evenly distributed.
04 - Pour the dark chocolate onto the prepared baking sheet and spread into an even rectangle approximately 8x10 inches using a spatula.
05 - Melt the white chocolate in a clean heatproof bowl using the same double boiler or microwave method, stirring until smooth and glossy.
06 - Stir the remaining peppermint extract into the melted white chocolate until well combined.
07 - Gently pour the white chocolate over the dark chocolate layer. Use a skewer or toothpick to swirl through both chocolates, creating a marbled pattern.
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 throughout.
10 - Once fully set, break the bark into irregular pieces and serve immediately or store for later.