Turn your Instant Pot onto Sauté on high. When the display reads HOT, add your ghee or oil. When the ghee is hot and shimmering, add add the oil, and spread it all around.
Pour in contents of the blender and allow it to cook for 10-15 minutes, stirring occasionally to prevent it from sticking. You're doing this in lieu of charring the vegetables ahead of time, so don't short cut this step. You want the mixture to cook well, to thicken and to smell a little smoky.
Add the chicken and the chicken broth, mix well, and set your Instant Pot to either its Poultry setting, or for 15 mins HP. Allow it to release pressure naturally.
When you open it, you'll probably see more liquid than you think you need. Don't worry, as this is about to get thicker.
Remove and shred chicken.
Turn the pot onto Sauté and whisk in the cream cheese. Taste to ensure the sauce is spiced right for you. Add a little extra cream cheese if you want it milder.
Once the cream cheese has melted, add the cut up corn tortillas and mix well. Turn off the pot.
Add the cheese and mix again and let the mixture rest. You want the tortillas to absorb the sauce and get soft.
Serve with some sour cream on the side, and add sliced avocados if desired.