Pull the leaves off your cauliflower and cut off the stem.
Put it on a rack in a big stockpot with about an inch of water in the bottom and bring to a boil. (If you're like me and don't have a rack, just leave enough stem for it to balance on and not quite sit directly in the water.)
Reduce to a simmer, cover and cook for approximately 20 minutes or until you smell it.
Meanwhile, mix 1 c. of mayo with 3 T of dijon mustard and 2-3 tsp. garlic powder. Mix well and then add the cheddar.
Remove the cooked cauliflower head to a baking dish, and spread on the mayo mix.
Broil long enough to melt the cheese and just barely begin browning parts of it.
Take out and use a knife to remove any remaining stem. It will be very soft and easy to do.
Then use a spoon to break the cauliflower up and mix the sauce in well. (If you've got any stem left, you'll find it during this step because it won't break up easily.)