Instructions

• Preheat the oven to 350°F. Line a quarter sheet pan (or a 9×13-inch cake pan) with parchment paper or spray it with nonstick baking spray.
• Place the 12 tablespoons softened unsalted butter and 1-1/2 cups packed brown sugar in the bowl of a stand mixer fitted with the paddle attachment.
• Beat on medium speed until the butter and sugar are well combined and creamed, about 1 minute.
• Add the 2 large eggs and 2 teaspoons pure vanilla extract. Mix to combine, stopping to scrape down the sides and bottom of the bowl as needed.
• Add 2 cups old fashioned oats, 1-1/2 cups all-purpose flour, and 1-1/2 teaspoons baking soda to the bowl. Mix on low speed just until the dry ingredients are incorporated; do not overmix.
• Add 2 cups chocolate chunks and fold them into the dough with a spatula until evenly distributed.
• Transfer the dough to the prepared pan and spread it into an even layer, pressing gently to level the top.
• Bake in the preheated oven for 28–30 minutes, or until the bars are golden brown around the edges and set in the center.
• If using flaky sea salt, sprinkle it over the bars immediately after removing them from the oven so it adheres.
• Allow the cookie bars to cool completely in the pan on a wire rack. Once cool, lift them from the pan using the parchment (if used), transfer to a cutting board, and slice into bars.