Line a baking sheet with parchment or wax paper.
Melt the semi-sweet chocolate and white chocolate in separate bowls. Stir in ½ teaspoon peppermint extract to the melted semi-sweet chocolate.
Pour the melted semi-sweet chocolate onto the prepared baking sheet and spread it into a thin(ish) layer. Next, drop spoonfuls of the melted white chocolate on top of the semi-sweet chocolate.
Using a toothpick or a butter knife, drag it through the chocolate and swirl it around until you get the marbling effect you like.
Sprinkle the holiday sprinkles and crushed candy canes bits into the chocolate. Then, press in the Oreo chunks lightly into the chocolate.
Pop in the fridge and let it chill for about 30 minutes, until the chocolate hardens completely. Enjoy!