Preheat oven to 350 degrees F. Bring a pot of water to a boil. Meanwhile, cut cauliflower into small pieces. Add cauliflower to pot and boil for 7 minutes, or until softened but not completely mushy. Drain well then add to a large bowl. Mash until almost smooth but some small lumps remain. Mix in cream cheese, sour cream, parmesan cheese, green onions and all but 3 tablespoons of the crumbled bacon. Mix well until fully combined.