Swirled Mascarpone Brownies with Hazelnuts

Ingredients (12)

• 1 1/2 cups unsalted butter
• 12 ounces 60% cocoa bittersweet chocolate
• 6 large eggs
• 1 tablespoon plus 1 teaspoon McCormick's Pure Vanilla Extract
• 1 2/3 cup sugar
• 1 1/2 cup all-purpose flour
• 1 teaspoon salt
• 1 1/2 cups chopped hazelnuts
• 1 egg yolk
• 1 tablespoon flour
• 2 tablespoons sugar
• 8 ounces mascarpone cheese