Preheat the oven to 400°F or 200°C.
Place butternut squash on a baking tray and bake for 45 minutes or until easily pierced with a fork.
Drizzle cauliflower with olive oil, salt, and pepper and roast for 40 minutes, or until cooked through and golden brown.
Place squash, nutritional yeast, mustard, milk, tahini paste, salt, pepper, and garlic powder in a food processor fitted with the 's' blade. Blend until smooth.
In a casserole dish, pour the sauce over the cauliflower. Broil for about 10 minutes.
Top with scallions.
Enjoy!
