Chocolate Cinnamon Brownies

INGREDIENTS

• 1/2 cup unsalted butter, softened PLUS
• 2 tablespoons unsalted butter, softened
• 1 cup white sugar
• 1 1/2 teaspoons vanilla
• 2 eggs
• 3/4 cup flour
• 1/2 teaspoon baking powder
• 1/4 teaspoon salt
• 1/4 cup unsweetened cocoa, PLUS
• 2 tablespoons cocoa
• 1/2 cup firmly packed brown sugar
• 1/2 cup chopped walnuts (or pecans)
• 1 tablespoon ground cinnamon