Spray a 9 x 13 inch pan with cooking spray or line with foil. In a large saucepan, heat the butter over low heat. Once the butter has melted, add the sweetened condensed milk, dark chocolate chips, and 1 cup of the Andes chips. Stir constantly until the chocolate has melted. Add the heavy cream ⅛th of a cup at a time and continue stirring until the chocolate no longer looks granulated and appears more glossy. It should look like thick, glossy, chocolate cake batter. You do not want it to be too thin. Remove from heat and add the salt and extracts. Pour the hot mixture into the prepared 9x13 pan and smooth. Top with remaining Andes chips. Refrigerate for several hours until set.
Recipe by Five Wooden Spoons at https://www.fivewoodenspoons.com/2013/12/23/dark-chocolate-mint-fudge/