Preheat oven to 450.
In a medium hot pan, cook chorizo until well done, drain if needed, and set aside.
Melt 2 Tbsp butter, and toss the cauliflower with it. Sprinkle with salt & pepper, then transfer to a baking dish. Roast 15 - 20 minutes, until crisp and tender.
Meanwhile, in a large bowl, whisk together sour cream, heavy cream, minced garlic, half the cheddar, green onions, and pepper.
Once cauliflower is done, add it to the sauce mix and blend well. Add chorizo, and return it all to the baking dish. Top with the remaining cheddar.
Bake for 5 - 10 minutes. Top with more green onions, and serve.