Preheat the oven to 350°F and butter a 3-quart casserole dish.
Fill a pot with about 1 inch of water and bring to a boil over high heat. Place the cauliflower in a steamer insert and place over the water. Cover with a lid and steam for about 5 minutes, or until cooked but still slightly crisp. (You do not want them soft and falling apart, as they will continue to cook when your casserole is baked). Transfer to a medium-size bowl.
In a blender, combine the cottage cheese, milk, and seasonings, and blend until smooth. Transfer the blended mixture to a medium size saucepan over low heat and bring to a simmer. Add the Cheddar, stirring continuously to melt. If the cheese sauce is not completely smooth, return it to the blender and blend until smooth.
Pour the cheese sauce over the cauliflower and toss to coat.
Transfer to the prepared casserole dish. Cover with aluminum foil and bake for 45 minutes. Remove the foil and top as desired. Bake for an additional 5 to 10 minutes, until hot and bubbly.