Chocolate Pavlova with Mousse & Fresh Berries

Ingredients

• 6 large egg whites -- room temperature (reserve the yolks)
• 1/8 teaspoon cream of tartar
• 1 pinch Kosher salt
• 1 1/2 cups white sugar
• 1 teaspoon vanilla extract
• 1/4 cup unsweetened cocoa powder
• 11 ounces bittersweet chocolate
• 3/4 cup heavy whipping cream
• 4 large egg yolks -- reserved from meringue
• 1/4 cup white sugar
• 1 tablespoon strong espresso
• 1 1/4 cups heavy whipping cream
• 2 cups hulled and quarter fresh strawberries
• 1 teaspoon sugar
• 2 teaspoons balsamic vinegar
• 1 cup crëme fraiche
• 1 ounce shavings of bittersweet chocolate