Microwave the frozen cauliflower, following package instructions, until it's very soft. Drain thoroughly and let cauliflower sit in a strainer for a minute, or pat it dry to remove excess water.
Transfer the hot cauliflower to a food processor. Pulse a few times to break up large pieces, scraping down the sides as needed.
Add cream cheese, salt, and pepper. Pulse again to incorporate, pausing if necessary to scrape down the bowl.
Slowly add the heavy cream, pulsing until the mash reaches your preferred consistency, smooth or slightly chunky. Taste and adjust seasoning if needed.
If the mash seems watery, pour the mixture into a saucepan and let it cook over low heat for a few minutes to allow excess moisture to evaporate.