In a large bowl, cream together butter and sugars. Add eggs and vanilla extract. Beat until fluffy, about 1-2 minutes.
In a separate bowl, whisk (or sift) together the flour, oat flour, salt, baking soda, cornstarch, and cinnamon. (If using quick cook oats, grind into a fine powder using a food processor or blender before adding to dry ingredients.)
Gradually stir dry ingredients into butter mixture until just combined.
Add chocolate chips and stir until just combined.
Cover bowl or wrap dough in wax paper. Chill for at least 1 hour (up to 24 hours) in the refrigerator. Refrigerating will help the flavors meld and also create a firmer dough to roll into balls.
Preheat oven to 350 degrees.
Remove dough from refrigerator and allow to sit at room temperature for 10 minutes. For jumbo size cookies, scoop dough using a 3 tablespoon large scoop (or use a medium 1.5 tablespoon scoop and combine two balls together).
Place cookie dough balls 4 inches apart onto a parchment lined baking sheet (I bake jumbo size cookies 6 at a time on a half sheet pan). Bake for 14-16 minutes, or until lightly browned around edges. Allow to cool for 5 minutes before removing to a wire rack to cool completely.
If making standard size 1.5 tablespoon cookies, place cookie dough balls 2 inches apart onto a parchment lined baking sheet. Bake for 10-12 minutes, or until lightly browned around edges.
If you can't find large chocolate chips, regular chocolate chips can be used instead.
Your cookies will keep for 5-7 days in a sealed container. To help keep cookies fresh, you can place a slice of bread in the container with the cookies. Replace the bread slice as needed.
You can keep raw cookie dough in the refrigerator for 3 days. Cookie dough balls (and baked cookies) freeze well, up to 3 months in a sealed plastic container or freezer bag. Allow frozen balls to thaw for up to 10 minutes on the baking sheet before baking, or add 1-2 minutes to the baking time.