Double Chocolate Brownies

Bahan-bahan (16 porsi)

• 6 tablespoons unsalted butter
• 6 ounces semisweet chocolate
• ¼ cup unsweetened Dutch-process cocoa powder
• ¾ cup all purpose flour
• ¼ teaspoon baking powder
• ¼ teaspoon salt
• 2 large eggs
• 1 cup granulated white sugar
• 2 teaspoons vanilla extract