Fudge Truffle Cheesecake

2 cups (12 oz. pkg) Semi-sweet choc. chips
3 pkgs. (8 oz. ea.) cream cheese, softened
1 14oz. can sweetened condensed milk
4 eggs
2 tsps. vanilla
1 prepared chocolate cookie crumb crust

Heat oven to 300. In heavy saucepan, over low heat, melt chips, stirring constantly. In large bowl, beat cream cheese till fluffy. Beat in milk until smooth. Add melted chips and remaining ingredients. Pour into prepared crust. Bake 1 hour and 5 minutes, until center is set.