Preheat oven to 375°F. Lightly grease an 8x8 baking dish.
While the oven is preheating, cut cauliflower into large florets. Place florets and garlic in a medium saucepan and cover with water. Bring to a boil on the stovetop; boil until tender, about 7 minutes. Drain.
Transfer cauliflower and garlic to a blender with half and half, melted butter and salt. Blend until combined. Blend in the cream cheese, then the egg; process until smooth.
Pour half the cauliflower batter into the prepared baking dish. Cut half of the cheese into small dices and spread evenly over the cauliflower in the pan. Pour the rest of the cauliflower over top the diced cheese.
Bake 25 minutes. Meanwhile, shred the remaining half of the cheese. After 25 minutes, remove pan from the oven, sprinkle shredded cheese evenly over top and return to oven. Bake an additional 15 minutes, or until slightly golden.
Cheese: Keep the cheese cold in the fridge until its time to dice it or shred it. It is much easier to slice and shred cold cheese.
Double: You can easily double this recipe and bake in a 9x13-inch pan. Or, double it and bake in two 8x8-inch pans so you have one to share or one to freeze for later!
Make-ahead: This cauliflower mash can be assembled and baked the day before, then reheated in the oven the next day.