Filling:
4 8-oz pkgs. cream cheese, softened
1 cup sugar
3 Tbs flour
4 eggs (room temperature)
1 cup sour cream
6-oz semi-sweet baking chocolate, melted
1 Tbs vanilla extract

Preheat oven 325° F.
Crust

Process graham crackers into fine crumbs.
Separately process walnuts into crumbs.
Combine graham crackers, walnuts and 1/4 cup sugar. Mix.
Add melted butter & mix.
Press into "bottom only" of "tall" 9" springform pan.
Bake 8 minutes. Set aside.
Filling

Preheat oven 350°
Combine cream cheese, sugar & flour.
mix at med speed w/ electric mixer until well blended.
Reduce speed to low. Add eggs on at a time mixing well after each addition.
Blend in sour cream, vanilla and melted chocolate; pour over crust.
IMPORTANT: Place springform pan on baking sheet. Bake 1 hour or until cake is almost completely set up in center.
Loosen cake from rim of pan by running knife around edge.
"Do not" release springform pan at this time. Cool.
Cover and refrigerate overnight.