Pavlova with Lemon Curd and Berries

INGREDIENTS

• 1 tablespoon cornstarch
• 4 cups mixed berries
• 3 large egg yolks
• 1/2 stick unsalted butter
• 1/8 teaspoon salt
• 3 tablespoons cold water
• 1 cup heavy cream
• 2/3 cup granulated sugar
• 1 cup superfine granulated sugar
• 1/3 cup fresh lemon juice
• 2 teaspoons grated lemon
• 3 large egg whites at room temperature 30 minutes
• 1 teaspoon distilled white vinegar