Combine graham cracker crumbs with melted butter. Press firmly into bottom of 9-inch springform pan. Refrigerate crust for 10 minutes to set while preparing filling. Beat softened cream cheese and powdered sugar together until smooth and creamy. Mix vanilla extract and 1/2 cup cold brew coffee into cream cheese mixture until combined. Whip cold heavy cream in separate bowl until stiff peaks form. Gently fold whipped cream into cream cheese mixture to create light, airy filling. Dip ladyfingers briefly into remaining 1/2 cup cold brew coffee – don’t oversoak. Layer coffee-soaked ladyfingers over chilled crust in springform pan. Spread cheesecake mixture evenly over ladyfinger layer, smoothing top. Cover and refrigerate for at least 4 hours or overnight until firm and set. Before serving, dust top generously with cocoa powder using fine-mesh sieve. Slice with sharp knife, wiping clean between cuts for neat slices. Serve chilled.