Beat the butter for 1 minute until fluffy. Add the sugars and the egg. Continue beating for another minute.
Add the vanilla, flour, corn starch, baking soda, walnuts, Chocolate chips, and rolled oats. Mix with a wooden spoon until all the ingredients are combined.
Using a 2 inch cookie scooper or with your hands, form 20 equal size balls. Place molds on baking sheet at least 2 inches apart.
bake for 8 or until the edges begin to darken. Do not over-bake because the cookies will firm up after cooling down.