Cut the cauliflower into florets and put it in a bowl with 1/4 cup of water and cover with plastic wrap. Microwave on high to steam it until tender, about 10 minutes.
Drain the cauliflower and puree it with the cream, egg, and white cheddar cheese until smooth. Set aside.
Brown the beef along with the onion and garlic powder, salt and pepper. Drain off any excess fat and discard the fat.
Turn the heat down to low and add the cream cheese, stirring until it is melted.
Add the Worcestershire sauce and sugar-free ketchup. Adjust the seasoning with salt and pepper.
Add the mashed cauliflower in a layer on the bottom of a 9x9 (or similar) casserole dish.
Add the ground beef mixture to the top and sprinkle with cheddar cheese.
Bake covered with foil at 375-F for about 15-20 minutes or until heated through and bubbly.
Top with diced pickle, tomatoes, and onions - all your favorite cheeseburger flavors. A bit of sour cream is perfect on the top, too!