Add butter, onion and garlic to instant pot. Set to saute and cook until onion is tender, about 3-4 minutes.
Add cauliflower, broth and seasoning. Place the lid on the instant pot and seal shut. Close the pressure release valve.
Set instant pot to manual, high pressure for 8 minutes. When cooking cycle is complete, quick release pressure. Carefully open pot and mash cauliflower.
Stir in cream cheese until melted. If necessary, return to saute mode to continue to heat.