Preheat oven to 275°F. Fit a piece of parchment paper onto a baking sheet.
Beat the egg whites in a stand mixer until they reach soft peaks.
Gradually add the sugar, a half a cup at a time and continue to whip until the whites form stiff peaks.
Fold in vinegar and cornstarch.
Spoon mixture onto the baking sheet, forming a large round evenly shaped mound. Think of an extra large hockey puck.
Bake for 1 hour, until the Pavlova is crispy on the outside and has a soft, marshmallow center.
Evenly spread the marmalade onto the top.
Whip the cream with the Grand Marnier and spread it on the marmalade. Enjoy!
» Metric Converter