Rice the cauliflower with a food processor or with any other old school method like a shredder. If we are after a bit drier hash brown it is recommended to remove some of the water that is in the cauliflower. This can be done by simply salting the riced cauliflower and let it sit for about 20 minutes. If we are in the rush we can steam it or simply toss the whole thing into the microwave oven for 2 minutes.
Shred the cheese in case if it's not shredded already.
Finely cut the onion up using a food processor or a trusty sharp knife with the roller technique.
Using a kitchen towel or cheese cloth squeeze out as much liquid as possible from the salted, steamed or microwawed shredded cauliflower.
Put all the ingredients into a big enough bowl and mix well together.
Make little apricot sized balls out of the mixture and place one batch onto a low to medium heat oiled or buttered frying pan.
Press them gently but firmly with a spatula so they take up a round shape. Make sure the oil is hot enough before spreading the balls out.
Fry each side on low to medium heat until golden brown. This should take about 5 minutes for each side. It tends to stick and burn so check regularly but carefully as it falls apart easily before a crust is formed. A spatula is a must for stainless steel frying pans.
Optionally cauliflower hash browns can be made in the oven too. Use a parchment paper and bake them until golden brown for about 30-40 minutes at 350°F / 180°C.