Place the cauliflower and potatoes into your KitchenAid® 4-Quart Multi-Cooker or slow cooker. Pour in the heavy cream, milk, and season with garlic, salt and pepper. Next, sprinkle the butter cubes evenly over the top.
Cover with the lid and set the Multi-Cooker to the “high” slow cooker setting for about 5 hours. After about 4 hours, remove the lid and, using a potato masher, mash the potatoes and cauliflower chunks. Everything will mash together very easily. Mix, taste and season with more salt and pepper if needed and cover with the lid again.
When the mashed potatoes are ready, change the setting to “keep warm” until ready to serve. Garnish with a little parsley when the mashed potatoes are in the serving dish. Enjoy and serve with some butter if desired.