ingredients 1/2 cup unsalted butter one 12-ounce b packed 3 large eggs 2 teaspoons vanilla extract 1/4 cup unsweetened natural cocoa powder 1 1/2 cups all-purpose flour 1 1/2 teaspoons baking powder 1/4 teaspoon salt about 8 ounces dark chocolate, diced into 1/2-inch pieces (i used a trader joe’s pound plu