Set the Instant Pot to sauté. Heat the oil and sauté the onion until soft, about 2–3 minutes. Add garlic and sauté for another 30 seconds. Don’t rush this step—flavor builds here.
Add the chicken pieces. Sear them lightly—just enough to get a bit of color. You don’t need to cook them through yet.
Pour in the chicken broth and canned tomatoes with their juice. Stir in the Italian seasoning, and season with salt and pepper to taste.
Lock the lid, set to manual/high pressure for 6–8 minutes depending on how done you like your chicken. Quick release or natural release as you prefer.
Open the pot. If you’re adding frozen vegetables, stir them in now and simmer on sauté for 2–3 minutes until warmed through. For extra creaminess, whisk in cream cheese or sour cream until smooth.
Taste, adjust seasoning, and serve hot. Easy peasy, right?