Heat Instant Pot to “Sauté.” Add oil, chicken, onion and celery; season with salt and black pepper Cook until chicken is no longer pink and onions are translucent, 6-8 minutes..
Add garlic and cook for 1 minutes or until garlic is fragrant.
Add chicken broth, diced tomatoes and hot sauce. Stir to combine, scraping all browned bits off the bottom of the pot. Add pasta, making sure pasta is submerged in liquid.
Set Instant Pot to “Manual” for 5 minutes. Turn valve to Seal. When the timer goes off, turn valve to Vent to Quick release the pressure.
Keep Instant Pot on Warm and add cream cheese, blue cheese dressing, and shredded mozzarella. Stir gently until cheese is melted. With Instant Pot remaining on Warm setting, let pasta rest for 10 minutes. It will thicken slightly.
Serve topped with blue cheese crumbles and green onions.
If you want to amp up the vegetables a little, you could add a diced sweet bell pepper or diced carrots when you sauté the chicken, onion, and celery.
To make ahead or turn into a freezer meal: Make as directed and then pour into a greased 9x13 pan and cover with foil. Freeze or refrigerate until ready to bake. Place cold pan in cold oven and preheat oven to 350°F. Cook for an hour, uncovering in the last 15 minutes, or until heated through. It may require slightly longer cooking time if frozen. If cooking from frozen, you can also thaw overnight in fridge before baking.