Preheat the oven: Set to 400°F. Pat turkey thighs dry and season with salt and pepper.
Make herb butter: In a bowl, mix softened butter, olive oil, garlic powder, thyme, rosemary, and sage.
Prep the turkey: Loosen the skin and rub half the butter mixture under it. Rub the rest on top of the skin.
Roast: Place on a baking sheet and roast 40–50 minutes, until golden and internal temperature hits 165°F.
Start the mash: While turkey cooks, steam or boil cauliflower until tender (about 10 minutes). Drain well.
Blend: Add cauliflower, butter, cream cheese, heavy cream, garlic, salt, and pepper to a food processor. Blend until smooth and creamy.
Make the gravy: Once the turkey is done, remove it and pour drippings into a pan. Add broth and cream, whisk over medium heat. Sprinkle xanthan gum if using and whisk until thickened. Season to taste.
Serve: Plate creamy cauliflower mash, top with sliced turkey, and drizzle generous amounts of gravy.