Line your cookie sheet with parchment paper or your reusable baking mat. Set aside.
In a food processor fitted with a steel blade, combine the brown sugar, oatmeal, and the regular sugar. Process 2/12 to 3 minutes, stop often to pulse, but grind until the oats are VERY finely ground.
Combine the flour, baking soda, and the salt in a medium bowl. Use a whisk if your flour is lumpy. Set aside.
In your stand mixer, combine your butter and the corn syrup on medium-low until the mixture is smooth, creamy, and combined (about a minute total).
Scrape the sides.
Add the oatmeal and sugar mixture in three additions and mix for 2 minutes. Scrape the sides on occasion.
Add in the eggs and the vanilla extract and combine for 1 minute. Scrape down the bowl as necessary.
Set the mixer speed to low and add in the dry ingredients one-half at a time. Mix ONLY until blended. Resist the urge to mix it to death!
Fold in the chocolate chips and the walnuts (if using) with a rubber spatula to avoid overmixing the dough.
Using a 1 1/2 Tablespoon cookie dough scoop like I did and you will have larger, though fewer cookies, than if you use a smaller 2 teaspoon-sized scoop. Drop the dough onto the sheets about 3" apart.
Scrape down the sides of the bowl so you better combine the chocolate chips and the nuts (if using).
Bake for 10-12 minutes (my oven took 11 minutes using a 1 1/2 Tablespoon scoop). Remove from the oven when the cookies look a light golden brown and like something you want to eat. Do not overbake the cookies.
Remove to wire rack to cool for 2 minutes.
Transfer to cooling racks to cool completely before storing in a reusable plastic container. These cookies may last up to 5 days or frozen.