Shred cauliflower with a cheese grater into hash brown shapes. Spread cauliflower hash browns in 9x13" baking dish. Mix onions, cheese, cream cheese, heavy cream and sour cream until completely mixed. Melt butter, mix with pecans and sprinkle on top. Bake at 350°F for 30 minutes. (or cook in crockpot for 10-12 hours)