01 - Line a baking sheet with parchment paper or a silicone mat to prevent sticking.
02 - Melt the semisweet chocolate in a heatproof bowl over a pan of simmering water or microwave in 30-second bursts, stirring each time until smooth. Stir in 1/2 teaspoon peppermint extract.
03 - Pour the melted semisweet chocolate onto the prepared baking sheet and spread into a rectangle approximately 9x12 inches.
04 - Melt the white chocolate using the same method. Stir in the remaining 1/2 teaspoon peppermint extract.
05 - Drop spoonfuls of the melted white chocolate over the semisweet base. Use a skewer or knife to swirl the two chocolates together for a marbled effect.
06 - Immediately sprinkle the green M&Ms or mint candies, green sprinkles, and mini chocolate chips evenly across the surface. Gently press the toppings into the chocolate.
07 - Refrigerate for at least 30 minutes until fully set. Break or cut into pieces before serving.