Line an 8-inch square pan with foil, allowing foil to extend over sides of pan. Spray with no stick cooking spray.
Melt chocolate as directed on package. Beat cream cheese in large bowl with electric mixer until smooth. Gradually beat in sugar on low speed until well blended. Add melted chocolate and vanilla; mix well. Stir in chopped nuts.
Spread evenly in prepared pan.
Refrigerate at least 1 hour or until firm. Use foil to lift out of pan onto cutting board. Cut into 25 squares or triangles. Store in refrigerator.