Tim Tam Pavlova

Preheat oven to 300°. Line a baking sheet with parchment paper and set aside. Using an electric hand mixer, beat whites while slowly adding sugar until stiff peaks form. Add cocoa powder, cornstarch, vinegar, and vanilla and beat until glossy and thick. Gently fold in all but 1⁄2 cup Tim Tams. Spread onto prepared baking sheet into a 10" x 8" rectangle, about 3" thick; reduce oven temperature to 250° and bake for 2 hours, or until cooked through. Turn off oven and let cool in oven with door ajar. Serve with whipped cream over the top and remaining Tim Tams sprinkled over.