Meanwhile, in large bowl, beat cream cheese, sugar and vanilla with electric mixer on medium speed until smooth. Beat in eggs, one at a time, just until blended. Divide batter between 2 bowls. Beat melted chocolate into 1 bowl; stir in 3/4 cup of the sour cream. Beat remaining 1/4 cup sour cream into second bowl; stir in chopped toffee candy. Pour toffee batter over crust. Carefully spread with chocolate batter.