Preheat oven to 350 degrees.
Fill a saucepan with water and heat until hot (not boiling or butterscotch morsels will get lumpy). Place butterscotch morsels and butter in second saucepan and set on top of first saucepan (or use a double boiler if you have one). Heat morsels and butter until they are smooth. Transfer the melted butterscotch morsels and butter into a bowl. By hand, stir in the graham cracker crumbs and nuts (optional) with a fork. Stir until the mixture forms small crumbs. Take out 2 cups of the crumb mixture and set aside for later. Press the remaining mixture into a 15" x 10" by 1" baking pan. Bake the crust at 350 degrees for 12 minutes.
In a mixer, combine cream cheese, sugar and beat until creamy. Add eggs and beat well. Blend in the flour and lemon juice. Remove the crust from the oven. Pour the cream cheese mixture into the crust. Smooth out evenly. Sprinkle the 2 cups of graham crackers that you set aside over the entire top of the cream cheese mixture. Bake at 350 degrees for 25 minutes. Cool completely and cut into squares. Chill before serving. Refrigerate leftovers.