Preheat oven to 400 degrees and place rack in the middle.
Cook pasta al dente in a large pot of salted water according to your box instructions. Drain and rinse shells with cold water until they are cool enough to handle.
In a mixing bowl, combine chicken, sour cream, cream cheese, buffalo sauce, salt, and pepper.
Grease your cast iron or baking dish with the olive or vegetable oil to avoid the shells sticking to your pan.
Spoon the mixture into each shell and arrange the filled shells in a cast iron pan (or a baking dish). Sprinkle mozzarella cheese on top and bake for 20-25 minutes.
My favorite dairy free substitutes for this recipe are: