Cappuccino Cinnamon Squares

INGREDIENTS

• :
• 1¼ cups plus 2 tablespoons sugar
• 1 tablespoon plus 2½ teaspoons ground cinnamon
• 1 tablespoon plus 1½ teaspoons instant espresso powder
• 1¾ cups all-purpose flour
• 2 teaspoons baking powder
• Pinch of salt
• ¾ cup whole milk
• 2 large eggs
• ½ teaspoon pure vanilla extract
• 1 stick plus 2 tablespoons (10 tablespoons) unsalted butter, melted and cooled
• 3 ounces bittersweet chocolate, finely chopped, or ½ cup mini chocolate chips
• 6 ounces bittersweet chocolate, finely chopped
• 2½ tablespoons unsalted butter, cut into 4 pieces