First, start by dicing the onion and celery and mincing the garlic cloves. Set aside for later.
Next, turn on the saute function on the Instant Pot and wait for it to heat up a bit.
Once the inner pot has warmed up, add in the butter and wait for it to melt.
Next, add in the chopped celery and onion.
Immediately add in the salt and crushed red pepper flakes and saute until onions are translucent in color.
Next, add in the minced garlic cloves and saute for 30 seconds.
Add in the flour and stir constantly to combine with the other ingredients for about 1-2 minutes.
Cancel the saute function and immediately add in the chicken broth and give everything a quick stir. Deglaze the bottom of the pot with your spoon if needed.
Next, add in the broccoli florets and close the Instant Pot lid. Cook on high pressure for 4 minutes.
Once the soup is done cooking, press the quick release button to release the pressure. You’ll know all the pressure has finished releasing once the pin on top drops.
Next, open the Instant Pot lid and use a potato masher to mash all of the ingredients inside the inner pot.
Add in the sharp cheddar cheese and heavy cream. Give everything a quick stir to combine. Taste test the soup and add more salt as needed.
Next, close the Instant Pot lid to cover the cream of broccoli soup. You don’t have to lock it. Simply place it on top and leave it closed for 5 minutes so the soup can thicken up.
Finally, top off with more cheddar cheese if desired, serve warm and enjoy. You can also press the keep warm function if you won’t be eating it right away!