Cut off the leaves, bottom stem, and cut the cauliflower into florets.
Add a batch of cauliflower florets to the processor and pulse. Don't overload the food processor.
Continue pulsing the food processor until the pieces of cauliflower have a texture similar to grains of rice.
Notes
If you don't want to use a food processor, you can use a box grater instead. Cut the cauliflower into florets and grate each one with a medium-sized box grater into a large bowl.