Cover bottom of 9-inch round pan with parchment or waxed paper. Spray with cooking spray; set aside. Microwave 4 oz. chocolate and butter in large microwaveable bowl on HIGH 1-1/2 to 2 min. or until both are melted and mixture is well blended, stirring after 1 min. Add dry jelly powder and sugar; mix well. Blend in eggs. Stir in flour and nuts. Pour into prepared pan.