Preheat your oven to 375°F (190°C). Grease a medium-sized baking dish and set aside.
In a large pot of boiling salted water, blanch the cauliflower florets for about 3-4 minutes until slightly tender but still firm. Drain and set aside.
In a medium saucepan over medium heat, combine the heavy cream, garlic powder, onion powder, salt, pepper, Dijon mustard, and nutmeg. Stir until well mixed. Gradually add the cheddar and Gruyère cheeses, stirring continuously until melted and smooth.
In the prepared baking dish, arrange the blanched cauliflower evenly. Pour the cheesy cream sauce over the cauliflower, ensuring all florets are covered. If using, sprinkle the breadcrumbs on top for added crunch.
Finally, sprinkle the grated Parmesan cheese generously over the top of the dish.
Bake in the preheated oven for about 25-30 minutes, or until the top is golden brown and bubbling.
Once baked, remove from the oven and let it sit for about 5 minutes. Garnish with chopped fresh parsley before serving.
Notes
For added flavor, use freshly grated nutmeg.
Keyword au gratin, cauliflower, cheesy, vegetarian