Mix the Dough: In a large mixing bowl, cream together 1/2 cup unsalted butter, 3/4 cup packed light brown sugar, and 1/4 cup granulated sugar using either a hand mixer or a stand mixer with the paddle attachment. Cream them until the mixture becomes light and fluffy, which should take around 2 minutes.
Incorporate the Wet Ingredients: Add 1 large egg and 1 tablespoon pure vanilla extract to the mixture. Beat them for about one minute or until fully combined. Set this mixture aside.
Add the Dry Ingredients: Sprinkle in 2 cups all-purpose flour, 2 tablespoons cornstarch, 1 teaspoon baking powderr, 1/2 teaspoon baking soda, and 1/2 teaspoon salt. Mix on medium until combined. The dough will be thick, which is exactly what you want for these cookies.
Add Chocolate Chips and Walnuts: Gently fold 12 ounces semi-sweet chocolate chips and 1/2 cup walnuts pieces into the dough using a wooden spoon. Avoid over-mixing to maintain a gooey texture.
Chill the Dough: Refrigerate the dough for about 30 minutes. This step helps the cookies keep their shape and allows the flavors to meld.
Meanwhile preheat the oven: While the dough chills, preheat your oven to 475°F. This high temperature ensures a perfect cookie texture, crispy on the outside and gooey on the inside. Line a large baking sheet with parchment paper. This step prevents the cookies from sticking and makes cleanup a breeze.
Form Cookie Dough Balls: Once the dough is chilled, scoop out 2 heaping tablespoons of dough and roll each portion into a ball. Place these dough balls on the prepared baking sheet, leaving about 2 inches of space between each.
Bake the Cookies: Bake for 7-8 minutes, or until the cookies are lightly browned on the outside and half-baked and gooey on the inside. The high oven temperature ensures this perfect texture.
Cool and Enjoy: Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a cooling rack. You can let the cookies cool for another 5-10 minutes before indulging in these gooey chocolate chip cookies. They are at their gooey best when still warm.