Process chocolate cookies in food processor until fine crumbs form. Mix with melted butter, sugar, and salt until mixture holds together when pressed.

Press cookie mixture firmly into bottom of 9-inch springform pan. Use measuring cup bottom to create even layer. Refrigerate while preparing filling.

Beat room temperature cream cheese with electric mixer until completely smooth and fluffy, about 3-4 minutes.

Gradually add powdered sugar and cocoa powder, beating until well combined with no streaks.

Mix in melted and cooled dark chocolate, vanilla extract, and salt until uniform in color.

In separate bowl, whip cold heavy cream to soft peaks. Don't overwhip.

Fold 1/3 of whipped cream into chocolate mixture to lighten, then gently fold in remaining cream in two additions.

Pour filling over prepared crust, smoothing top with offset spatula. Cover with plastic wrap and refrigerate at least 4 hours or overnight.

For web design: Heat 1/3 cup cream until simmering, pour over chopped white chocolate. Let sit 2 minutes, then stir until smooth. Add corn syrup if using.

Pipe white chocolate ganache in spiral pattern from center outward. Use cocktail stick to drag from center to edge in 6-8 lines, creating web effect.

Garnish with food-safe plastic spiders if desired. Serve chilled.