Line an 8-inch square baking pan with parchment paper and set aside.
In a medium saucepan over low heat, melt white chocolate chips and sweetened condensed milk together until smooth, stirring constantly.
Remove from heat and stir in peppermint extract and green food coloring, if using.
Fold in chopped Mint Oreo cookies and Andes mint chips.
Pour the mixture into the prepared pan and spread evenly.
Refrigerate for at least 2 hours or until fully set.
Cut into small squares and serve chilled.