Boil a little water in a large pot, just enough to cover the bottom, then put a steamer basket in the pot, fill it with the cauliflower florets and put on the lid. Steam for 4 minutes.
In a large skillet, cook the bacon to your liking, then chop the bacon and set it aside, reserving the fat.
In a food processor, process the steamed cauliflower until it's a mashed consistency, then with the machine running, pour in the cream through the feeder tube.
Put mashed cauliflower into a serving bowl, stir in butter, a drizzle of the bacon fat, the horseradish, the cheese, then season to your liking with the salt. Top with scallions and bacon and serve.