Wash and cut the cauliflower into small bouquets. Cook for 15 minutes in a large pot of water. At the end of cooking, drain the cauliflower and set aside.
Cut the onion into small pieces and brown them in a pan.
In a blender, put the cauliflower, the onion, the heavy cream, the cheese, salt and pepper. Mix until you get a very smooth and creamy dough.