Preheat oven to 350 degrees Fahrenheit.
Line a baking tray with parchment paper and set aside.
In a large mixing bowl or stand mixer add melted butter and sugars and cream together with a paddle attachment or wooden spoon until light and fluffy. About 2-3 min.
Add in the egg and vanilla extract. Mix until fully combined.
In another bowl add flour, oats, baking soda, salt, cinnamon, and cornstarch. Using a fork, give the dry ingredients a quick mix until combined.
Take the dry ingredients and pour carefully into the wet ingredients.
Using a rubber spatula, fold the dry ingredients into the wet ingredients. Do not over mix. Stop mixing the moment the last bit of flour disappears.
Throw in the butterscotch chips and white chocolate chips. Mix into the dough until evenly dispersed.
Cover the dough with plastic wrap and let the dough rest for 20 min at room temperature. This step is important because it allows the oatmeal to absorb some of the wet ingredients, so the cookies don’t go flat while baking.
Using a large (3-4 oz) cookie scoop, scoop no more than six dough balls at a time to place on the prepared baking tray for baking.
If you would like, add a few more white chocolate and butterscotch chips to the tops of the cookie dough balls before baking.
Sprinkle the tops of the dough with Flakey Sea salt and bake the cookies at 350 degrees Fahrenheit for 10-12 min.
Repeat this process until all the cookies are baked.
Cool and Enjoy!