Set Instant Pot to sauté and heat ¼ cup vegetable oil.
Whisk in ¼ cup flour, stirring constantly for 10-15 minutes.
Cook until roux turns chocolate brown and smells nutty.
Add chopped onions, bell peppers, and celery; stir for 5 minutes.
Add minced garlic and sauté for 1 minute until fragrant.
Stir in diced tomatoes, Cajun seasoning, bay leaves, salt, and pepper.
Simmer the mixture for 2-3 minutes to meld flavors.
Add diced chicken thighs and stir to coat in the mixture.
Pour in 4 cups chicken broth, scraping the pot's bottom.
Close the lid, set steam release to sealing, and cook on high for 10 minutes.
Perform a quick pressure release and add peeled shrimp.
Set to sauté for 3-5 minutes until shrimp are pink and opaque.
