Yield: 8-inch round cake
Preheat oven to 300 degrees F. Line baking sheet with parchment paper. Trace 7-inch cake round on another piece of parchment paper. Cut out 9-inch square around traced circle. Place trace-side down on lined baking sheet. Set aside.
In the bowl of a stand mixer fitted with a whisk attachment, beat egg whites at medium speed until stiff peaks. Add sugar one tablespoon at a time. Once all the sugar has been added, increased speed to medium-high. Continue to beat until stiff peaks. At this point, meringue should be thick and glossy.
Add cocoa powder, cornstarch, and vinegar. Fold in using a large spatula until there are no longer any streaks of cocoa powder. Dollop meringue on prepared baking sheet. Use a spoon or mini spatula to distribute meringue into a round mound, using the traced circle as guidelines. The cooked meringue will expand slightly out of traced circle.
Bake 65-70 minutes. Do not open the oven during baking. After 60 minutes, open oven to check that meringue is dry on the outside. Turn off oven and allow to cool in oven for an hour. After one hour, prop oven door open using a wooden spoon and allow to cool for another 30-45 minutes.
Pour chilled heavy cream and maple syrup into a cold mixing bowl. Use an electric hand mixer to whip cream to soft peaks. Switch to a whisk and continue beating cream to medium stiff peaks. Fold in pinch of salt. Use immediately or store in the fridge.
Once pavlova has completed cooled, remove parchment square from lined baking sheet. Gently peel parchment from pavlova and place directly on serving plate.
Just before serving, top pavlova with maple whipped cream. The top of the pavlova will crack and fall from the weight of the cream. Sprinkle toasted pecans on top and drizzle additional maple syrup, if desired. Serve immediately.