Cook pasta 2 minutes short of package directions and drain.
In large saute pan, heat oil over med/high heat and add celery and onion. Cook until softened, then add diced garlic and cook for 1 minute more.
Add diced/shredded chicken, cream of chicken soup and peas. Stir to combine. Add the heavy cream, sour cream and 1 and 1/2 cups of the shredded cheddar cheese. Add salt and pepper to taste. Stir and heat through until starting to bubble and cheese is melted.
Add the cooked pasta to the pan and stir until all of the ingredients are combined.
Spread mixture into a 2 qt casserole dish that has been sprayed with non-stick cooking spray. Sprinkle remaining 1/2 cup (or more which I always do) on top.