Turn on the Sauté function. Melt the butter, then add the onion and celery and sauté until softened, about 3-5 minutes.
Turn off the Sauté function, then add the minced garlic and sauté it for about a minute in the residual heat.
Pour in a small amount of broth and use a flat-bottomed turner to scrape up any food that's stuck to the bottom of the insert. This will help prevent a burn warning. There shouldn't be much to scrape up with this recipe.
Pour in the remaining broth, then sprinkle in the dried dill. Layer the cauliflower florets evenly on top.
Close the lid and set the vent to sealing. Pressure cook on Manual High pressure for 8 minutes with the keep warm setting on (your Instant Pot may have a "Pressure Cook" button rather than a "Manual" button, depending on the model). It will take up to 15 minutes to come to pressure.
At the end of cooking time, quick release the pressure. I like to use a wooden spoon in case there's splatter. You can let it out in short bursts to reduce splatter (this is called a controlled quick release). Leave the keep warm setting on so that the dairy ingredients can warm up more easily.
Use an immersion blender to blend the soup right in the Instant Pot, until smooth and creamy.
Stir in the grated cheese, then the sour cream and half and half. Season with salt and pepper to taste.
Serve immediately topped with your favourite garnishes. Store any leftovers in a sealed container in the refrigerator and eat within 4 days. Can be frozen for up to 3 months.
Video
Notes
Inactive time indicates the time it takes for the Instant Pot to come to pressure and release pressure.
This recipe was tested in a 6-quart Instant Pot model.
Nutrition estimate does not include toppings (because this is variable based on how much you add!)