Preheat oven to 350 degrees.
Combine over hot (not boiling) water the butterscotch chips and butter. Heat until melted and smooth. Stir in graham cracker crumbs and nuts with a fork until mixture forms coarse crumbs. Reserve 1 cup crumb mixture for topping. Press remaining mixture into a 9" square baking pan. Bake at 350 degrees for 12 minutes.
In large bowl, combine cream cheese and sugar; beat until creamy. Add eggs, one at a time, beating well after each addition. Blend in flour and lemon juice. Pour evenly over hot baked crust. Sprinkle top with reserved crumb mixture. Bake at 350 degrees for 25 minutes.
Cool completely; cut into 2 1/4" x 1" bars. Refrigerate any leftovers.