Start by placing the 14 tablespoons of unsalted butter in a saucepan over medium heat. Stir continuously as the butter melts and begins to foam. Keep an eye on it as it transitions from clear to golden brown, and finally to a rich amber color. This process usually takes about 5-7 minutes. Once browned, remove it from heat and let it cool to room temperature.
In a large mixing bowl, whisk together the 2 and 1/4 cups of all-purpose flour, 1 teaspoon of baking soda, 1/2 teaspoon of ground cinnamon, and 1/2 teaspoon of kosher salt. Set aside.
In another bowl, combine the cooled brown butter with 1 cup + 2 tablespoons of dark brown sugar and 1/2 cup of granulated sugar. Mix well until the sugars are fully incorporated.
Add 2 large eggs and 1 tablespoon of vanilla extract to the butter-sugar mixture. Beat until smooth and creamy.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. If the dough seems too wet, add flour one tablespoon at a time until the desired consistency is reached.
Gently fold in the 2 cups of semi-sweet chocolate chunks and the 3/4 cup of toasted walnuts until evenly distributed throughout the dough.
For the best flavor and texture, cover the dough and refrigerate for at least 30 minutes. This step allows the flavors to meld and results in chewier cookies.
Preheat your oven to 350°F (175°C). Line your baking sheets with parchment paper.
Using a cookie scoop or spoon, drop generous amounts of dough onto the prepared baking sheets, spacing them about 2 inches apart. Sprinkle a pinch of flaky sea salt on top of each cookie before baking. Bake for 10-12 minutes, until the edges are lightly golden but the centers remain soft.
Remove the cookies from the oven and let them cool on the baking sheet for 5 minutes before transferring to a cooling rack. Enjoy them warm for the ultimate gooey experience!
