Hit Saute on your Instant Pot, add 1 tbsp of oil, and let the pot heat up. Add Carrots, Onions, and Shallot and saute until the onions and shallots are translucent and starting to get some color on them.
Add Broccoli and Cauliflower Florets, Chicken Broth, and Milk to the instant pot and then bring to a boil.
Turn off your Instant Pot, put the lid on and make sure the vent is in the "sealed" position. Then, cook the soup on High Pressure for 5 minutes
Once the timer goes off, let the soup naturally release for 5 minutes
Use an immersion blender and blend the contents of the pot until super creamy. Alternately, you can add it to a vitamix. If you prefer your soup to be chunky, then you can remove some florets before you blend the soup and then add them back afterwards.
Slowly add the cheese to the instant pot and stir continuously. Keep a small amount of cheese to the top each bowl of soup. Optional: add a little bit more milk and stir.
Add the reserved florets back in the instant pot, and serve immediately.