Start by preheating your oven to 350°F (175°C). This ensures that it reaches the perfect temperature while you’re preparing the cookie dough.

In a large mixing bowl, use an electric mixer (or a hand whisk) to cream together the softened butter, granulated sugar, and brown sugar. Beat until the mixture is light and fluffy, about 2-3 minutes.

Once the butter and sugars are creamed, add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract. The wet ingredients should now be smooth and slightly fluffy.

In a separate bowl, whisk together the flour, baking soda, and salt. Slowly add the dry ingredients into the wet mixture, mixing until just combined. Be careful not to overmix, as this can lead to tougher cookies.

Once your dough is formed, fold in the rolled oats, chocolate chips, and chopped walnuts (if using). The dough will be thick, but that’s exactly what you want for soft, chewy cookies.

Using a cookie scoop or a tablespoon, portion out the dough onto a parchment-lined baking sheet. Make sure the dough mounds are spaced about 2 inches apart to allow room for spreading during baking. Gently flatten the dough balls if you prefer a slightly thinner cookie.

Place the cookies in the preheated oven and bake for 12-15 minutes, or until the edges are golden brown. The center will still be soft, but the cookies will continue to firm up as they cool. For softer cookies, you can take them out a minute earlier.

Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. This ensures they set properly and stay intact.