1/2 cup unsalted butterone 12-ounce bag semi-sweet chocola packed3 large eggs2 teaspoons vanilla extract1/4 cup unsweetened natural cocoa powder1 1/2 cups all-purpose flour1 1/2 teaspoons baking powder1/4 teaspoon saltabout 8 ounces dark chocolate, diced intoâ 1/2-inch pieces (i used a trader joe's pound plus dark