Turn the Instant Pot to sauté mode and heat the butter or oil. Add the onions and cook until they begin to brown, about 2-3 minutes. Stir in the garlic and cook for 30 seconds.
Add the chicken, chicken stock, broccoli, cauliflower rice, and salt to the Instant Pot. Close the lid, set the sealing valve, and select manual – high pressure – for 1 minute.
Allow the Instant Pot to come to pressure. Once the cooking cycle is complete, do a quick release of the pressure. This process takes about 15 minutes in an 8-quart Instant Pot.
Stir in the cream cheese and shredded cheddar cheese until fully combined.
Optional Step: Transfer the mixture to a casserole dish, sprinkle extra shredded cheese on top, and broil for 3 minutes until melted and slightly golden.
Serve warm and enjoy!