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 Monterrey Jack, cream cheese, and heavy cream.
Stir in sliced green onions, chopped bacon, and garlic.
Drain any liquid from steamed cauliflower and add 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 Monterrey Jack cheese.
Cover dish with foil and bake for 25 minutes; remove foil and continue to bake until cheese is brown and bubbly.