Preheat your oven to 400F and place a rack near the top of the oven.
Whisk together the flour, cornstarch, salt, cinnamon and baking soda.
In a separate bowl, cream together the butter and sugar until fluffy, about 4-5 minutes. Once that is fully creamed add the vanilla and the egg and beat until combined.
Add in your oats to the wet ingredients and stir until combined. Then fold in the flour. Mix until no dry pockets remain.
Fold in your raisins then scoop into 5-6 mega cookies weighing about 150g each.
On a parchment lined baking sheet bake your cookies for 9-10 minutes on the top rack. After 10 minutes, begin checking every minute and take the cookies out when they are golden brown.
Let them cool for 30 minutes before eating.