Lightly coat a 9x13" casserole dish with non stick cooking spray, set aside.
Pre heat oven to 350 degrees F.
In a large pan melt 8 tbsp of butter over medium heat. Once it's melted add the green onion and jalapeno, stir and cook for about 2 minutes. Add the cream cheese, sour cream, cream of chicken soup, salt and pepper. Stir until smooth and begins to slightly bubble. Add the cheddar cheese and stir until melted. If your pan is large enough, add the potatoes right to the cheese mixture and stir to coat, then transfer to the casserole dish. If it's not large enough, place potatoes in a large bowl, add the cheese mixture and stir to coat, then transfer to the casserole dish.
Melt the remaining 5 tbsp butter. Place the crushed corn flakes in a medium size bowl and coat with the melted butter. Spread on top of the potato casserole.
Bake for 45-50 minutes or until hot and bubbly all over.
Can be made ahead of time - prepare as indicated above, but do not bake. Cover and place in fridge or freezer until ready to bake. You will need to increase the baking time an extra 10-15 minutes or until the casserole is hot and bubbly all over.