Preheat the oven to 350 degrees F (175 degrees C). Gather all ingredients.

Line bottom and sides of a 13x9-inch baking pan with heavy-duty aluminum foil, leaving a 2-inch overhang on all sides, lightly spray with baking spray; set aside.

Beat together white sugar, brown sugar, and butter with a stand mixer fitted with paddle attachment on medium speed until light and fluffy, about 3 minutes, stopping to scrape down sides as needed.

With mixer running on low, add eggs, one at a time, beating until just combined after each addition. Beat in vanilla until just combined.

Whisk together flour, baking powder, salt, and baking soda in a medium bowl until combined. With stand mixer running on low speed, gradually beat in flour mixture until almost fully incorporated, about 2 minutes, stopping to scrape down sides as needed.

Stir in chocolate chips and toasted walnuts until combined.

Transfer dough into prepared baking pan, spreading into an even layer.

Bake in preheated oven until golden brown and set, about 40 minutes, rotating baking pan front to back halfway through.

Let cookie cool completely in pan on wire rack, about 1 hour. Using foil overhang as handles, lift cookie out of pan.