Preheat oven to 350 degrees.
Steam cauliflower florets until tender.
While cauliflower steams, cream together 6 oz of the shredded cheddar, 6 oz of the Monterey Jack, cream cheese, and heavy cream.
Stir in sliced green onions, chopped bacon, and garlic.
Drain any liquid from steamed cauliflower and add hot cauliflower to cheese mixture.
Stir cauliflower and cheese mixture together.
Taste for seasoning, and add as necessary.
If you want a finer texture, give a few mashes with the potato masher.
Pour into a 2-3 quart casserole and sprinkle on remaining cheddar and Monterey Jack cheese.
Cover dish with foil and bake for 25 minutes; remove foil and continue to bake until cheese is brown and bubbly.