Drain the cooked cauliflower thoroughly in a colander. Let it sit for 5 minutes to allow excess steam and water to escape. This step is key for creaminess.
Transfer the drained cauliflower to a food processor or use an immersion blender. Add the butter or oil, cream, garlic paste, salt, and pepper.
Process until completely smooth and creamy. Stop and scrape down the sides as needed.
If using, pulse in the Parmesan cheese until just combined.
Taste and adjust seasoning before serving hot.
Notes
For the creamiest texture, press the cooked cauliflower through a potato ricer after draining before blending.