Set your oven to 350°F (175°C) and grease a 9 x 13-inch baking dish or line it with parchment paper.
In a large mixing bowl, use an electric mixer to beat the butter, white sugar, and brown sugar together for 3 minutes until light and fluffy.
Scrape the sides of the bowl, then beat in the eggs one at a time. Add the vanilla extract and continue mixing for another 3 minutes until smooth.
In a separate bowl, whisk together the flour, baking soda, and salt.
Slowly add the dry ingredients to the wet mixture, beating on low speed until just combined. Avoid overmixing.
Gently stir in 1 ½ cups of the chocolate chips and the chopped nuts (if using).
Transfer the dough to the prepared dish, spreading it evenly with a spatula. Press the remaining ½ cup of chocolate chips on top.
Place the baking dish in the oven and bake for 25-30 minutes, or until the top is light golden brown and the edges start to pull away. Do not overbake for a chewy texture.
Let the cookie bars cool completely in the pan on a wire rack. Once cool, slice into squares and serve.