EASY CHOCOLATE CHIP COOKIES

1/2 cup salted butter (see note) 1/2 cup brown sugar 1/2 cup white sugar 1 whole egg 1 1/4 cup all-purpose flour 1/2 teaspoon baking soda 1 cup chocolate chips 1/2 cup walnuts, coarsely chopped (optional) Note: If using unsalted butter, add 1/4 teaspoon iodized salt into the flour mixture