1/3 c. butter, melted
1 1/4 c. graham cracker crumbs
1/4 c. sugar
3 (8 oz.) pkgs. cream cheese, softened
1 (14 oz.) can sweetened condensed milk (not evaporated milk)
1 (12 oz.) pkg. semi-sweet chocolate chips, melted
4 eggs
2 tsp. vanilla

Preheat oven to 300 degrees. Combine butter, crumbs, and sugar. Pat firmly on bottom of 9 inch spring-form pan. In large mixer bowl, beat cream cheese until fluffy. Add milk; beat until smooth. Add remaining ingredients; mix well. Pour into pan. Bake 1 hour 5 minutes. Cool to room temperature; chill. Remove sides of pan. Refrigerate.