Switch on the Instant Pot to Saute mode.
Heat 1 tbsp of olive oil or butter in the inner cooking pan. Allow the butter to melt if you are using any.
Add onion and garlic and stir fry for about 1 minute.
Add cauliflower, potatoes, celery, rosemary and salt.
Mix well. Cover the Instant Pot but not tightly. Just place the lid over it.
Allow the vegetables to 'sweat' for about 2-3 minutes, with the IP still on saute mode.
Take the lid off.
Add water or vegetable stock and the milk. Stir gently to mix. If you are using cream then add it later.
Switch off the saute mode.
Cover the Instant Pot properly with the lid. Make sure the valve is set to sealing setting.
Switch on the Soup setting. Reduce the time to 7-10 minutes as this is a vegetable soup.
Allow the soup to cook. When the cooking time is over, move the valve to venting side.
Allow the pressure to reduce naturally.
Open the lid of the Instant Pot.
With a stick blender, blend the soup to a smooth consistency.
Switch the Instant Pot to the Saute mode.
This will allow the cauliflower soup to heat up.
Add the grated cheddar cheese and cream if you are using any.
Keep stirring the soup to melt the cheese.
Add pepper powder. Mix well
Cheesy Cauliflower Soup is ready.
Spoon the soup into soup bowls.
Add some cheddar cheese cubes and serve.
Enjoy the soup with your favourite bread.