Preheat oven to 350 degrees. Microwave morsels and butter in medium, uncovered, microwaveable bowl. On medium-high power for 1 minute; stir. Morsels may retain some of their original shape. If necessary, microwave at additional 10 to 15 seconds intervals, stirring just until morsels are melted. Stir in crumbs and nuts. Reserve 2 cups crumb mixture; press remaining mixture into ungreased 15 x 10 inch jelly roll pan. Bake for 12 minutes. Beat cream cheese and sugar in large mixer bowl until creamy. Add eggs one at a time, beating well after each addition. Beat in flour and lemon juice. Pour over crust; sprinkle with reserved crumb mixture. Bake for 20 to 25 minutes or until set. Cool in pan on wire rack. Cut into bars or diamonds; refrigerate.