Preheat oven to 400 degrees F.
Remove frozen cauliflower and place it on a lined baking sheet.
Place a head of garlic on the same baking sheet as well (trim off the top).
Massage olive oil, salt, pepper, and Italian seasoning onto cauliflower.
Roast in the oven for 45 minutes or until the cauliflower has browned. Garlic should also be soft.
Remove from oven and immediately place cauliflower in a pot.
Remove 5-6 roasted cloves from the head of garlic.
Place cloves of roasted garlic in the pot.
Add butter to the pot.
Turn heat on low-medium so the butter melts a bit. Turn off heat when butter is done melting.
Use an immersion blender to blend everything in the pot until smooth.
If you don’t have an immersion blender, place everything from the pot into a blender or food processor and blend until smooth.
Remove into a serving dish. Garnish with chopped chives, and extra butter if desired.
Serve hot!