Break apart the head or cut into florets, removing the stem.
Bring a large pot of water to a rolling boil. Set up a bowl of ice water.
Add cauliflower to the boiling water and boil for 3 minutes. Don't overcrowd the pot. Cook in batches if needed.
Once the time is up, strain the florets through a colander or scoop pieces out of the water with a slotted spoon and immediately add to the ice water for two minutes.
Strain again and set aside to drain. Pat dry with a clean towel.
Line a rimmed baking sheet with parchment or a silpat.
Add the cauliflower to the baking sheet without crowding the tray and place the tray in the freezer.
Freeze for three hours.
Break apart any clumps that have formed on the baking sheet and transfer to freezer-proof storage.
Notes
There is no need to thaw before adding to dishes.
Store unblanched in the freezer for up to two months, or blanched for up to 12 months.