Preheat oven to 180ºC . In a small saucepan, combine half c milk and the mint-chocolate chips. Cook over low heat, stirring constantly, until chips are melted and mixture is smooth. Set aside. In a large bowl, combine remaining 1 c of milk, condensed milk, and eggs; beat until well blended. Add chocolate mixture; beat well. Pour into a 1 litre casserole. Fill a 13 x 9 x 5 cm baking pan with 4 cups of water. Place casserole in baking pan. Bake at 180ºC . for 50 to 55 minutes. Serve warm or cool completely.