Preheat your oven to 400°F (200°C).

Break down the cauliflower into bite-sized florets, toss with olive oil, salt, and pepper, then roast for 15-20 minutes.

Melt butter in a saucepan, add garlic if using, whisk in flour, then gradually add milk and stir until thickened. Remove from heat and stir in cream cheese, salt, pepper, and mustard until smooth.

Combine roasted cauliflower with cheese sauce in a mixing bowl.

Pour mixture into a greased casserole dish, top with additional cheese, and bake for 20-25 minutes.

Broil for 1-2 minutes for a crispy topping, watching to prevent burning.

Let cool for a couple of minutes before serving.