cook the cauliflower
Place a pot filled with 1,5 L salted water over medium heat. Bring to a boil. Cut the cauliflower to 2 cm / 1-inch large chunks. Add to the boiling water and cook for about 10 minutes (low simmer). Drain and leave in a colander for about 5 minutes for the steam to evaporate from the cooked cauliflower.
Add the rest of the ingredients
Transfer the cauliflower to a blender or to a bowl if you will be using a hand-held immersion blender. Add the ground nutmeg, pepper, salt, heavy cream and butter.
Blend into a silky mixture
Blend everything into a blend, glossy mashed cauliflower. Pause the blender or immersion blender every now and then, scrape the sides of the bowl and continue to blend. Blend for about 5 minutes to get a really nice, glossy mixture. Season to taste with salt and pepper.
Serve or store
Serve the mashed cauliflower or store them in a fridge for up to three days. Before serving, reheat it. You can also store the cold mash in a freezing bag and store for up to a month in a freezer.