Cost per Serving:
Preheat oven to 350°F. Line bottom of a deep, 8-inch springform pan with parchment. Mist paper and pan with cooking spray. Wrap outside of pan with a double layer of foil. In a bowl, mix cookies and butter; stir until moistened. Press evenly into bottom of pan. Bake crust for 10 minutes; cool on a rack. Lower oven temperature to 325°F.
Using an electric mixer on medium-low speed, beat cream cheese, sugar, flour and vanilla until combined, scraping inside of bowl. Add eggs in 2 batches, beating just until blended after each. Fold in sour cream. Spoon batter gently into pan.
Place pan in a larger roasting pan; fill outside pan with hot water until it comes halfway up side of springform pan. Bake cake until it just appears to be set, but center is still slightly jiggly, 60 to 70 minutes. Remove pan from water bath and place on a rack. Run a small knife around inside edge of pan to loosen cake. Cool to room temperature; cover and refrigerate until firm, 8 hours.
Place chocolate in a warm spot in kitchen for 1 hour to soften slightly (don't let it melt). With a vegetable peeler over waxed paper, shave as much chocolate as possible into curls. Refrigerate until ready to use.
To serve, remove rim from pan and place cake on platter. Sprinkle chocolate curls on top.