Allow cream cheese and butter to soften. Cream butter and sugar. Add flour, cream cheese, and vanilla. Kneed until well mixed. Separate dough into equal halves. Put half in refrigerator while working on the other half. Take half of dough and roll out into a rectangular shape between two lengths of waxed paper. Melt half of chocolate chips with 2 tablespoons butter. Carefully spread chocolate mixture immediately over the dough. Roll up tightly and refrigerate at least two hours. Repeat with second half of dough.