Instructions

• Preheat the oven to 325°F (162°C). Line a 9×13-inch baking pan with aluminum foil and spray the foil with cooking spray; set the prepared pan aside.
• In a medium saucepan, combine 2/3 cup unsalted butter, 1 1/2 cups granulated sugar, and 1/4 cup water or coffee. Place over medium heat and bring to a simmer, whisking nearly continuously until the butter has melted and the sugar has dissolved (a slight graininess is okay).
• Remove the saucepan from the heat. Add 12 ounces (one 12-ounce bag) of the semi-sweet chocolate chips and whisk until the chips have melted and the mixture is smooth.
• Pour the chocolate-butter mixture into a large mixing bowl and let it cool for 1–2 minutes (warm but not piping hot).
• Add 4 large eggs and 1 to 2 teaspoons vanilla extract to the warm chocolate mixture. Whisk vigorously until the batter is smooth and shiny.
• Add 1 1/2 cups all-purpose flour, 1 teaspoon baking soda, and 1/2 teaspoon salt to the bowl. Gently stir or fold just until the dry ingredients are combined into the batter; do not overmix.
• Stir in the remaining 12 ounces (the second 12-ounce bag) of semi-sweet chocolate chips until evenly distributed.
• Pour the batter into the prepared 9×13 pan and spread it into an even layer.
• Bake on the center oven rack for about 45 to 50 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs but no wet batter. Avoid overbaking if you prefer fudgier brownies.
• Remove the pan from the oven and let the brownies cool in the pan for at least 30 to 60 minutes before slicing and serving (cooling longer makes neater slices).