In the Instant Pot combine the chicken broth, broccoli, carrots, onion, garlic and spices.
Cover and cook on Manual (so this is pressure cooking) for 4 minutes (choose high if you have this option). Then allow for 6 minutes NPR before releasing the pressure manually. During this time make the cornstarch/water slurry...whisking occasionally.
Remove the lid when the pressure is gone, and slowly stir in the heavy cream. Turn on Saute. You will need to stir this constantly until it's nearly ready to bubble (you will feel bubbles forming at the bottom) and then turn it off (I unplugged it). Don't let it scorch or boil.
Add your cheeses while you continue to stir and then the cooked rice. Do not stop stirring. You will then slowly add your slurry. You are wanting to thicken up the soup, you will likely not need to add the entire amount but you don't want to have to make more, so a little extra works better.
Serve with breadsticks, tortilla chips, rolls or even a bread bowl would be amazing!