Califlower “Mac and Cheese” Casserole

2 bags frozen cauliflower 1 cup Heavy cream (Slightly <1 cup if you prefer less creamy) 4 oz. cream cheese cut into small pieces (I recommend reduced fat) 1  1/2 tsp Dijon mustard 2 cups sharp cheddar cheese shredded (I recommend reduced fat) 1/4 tsp black pepper...