To prepare filling, combine chocolate chips, four ounces sweetened condensed milk, and vanilla extract in small saucepan. Cook until melted and smooth. Spread onto bottom of crust; set aside. Preheat oven to 350. In a mixing bowl, combine remaining sweetened condensed milk, cream cheese, egg, peppermint extract, and green food coloring Mix until smooth. Pour over chocolate layer in crust. Bake for 25 minutes, or until center is nearly set. Cool. Chill for three hours before serving.