Preheat the oven to 400°F.
Add the cauliflower to a large pot and fill to 1 inch with water.
Bring to a boil, cover, and allow to simmer until the cauliflower is tender but still firm, about 10-15 minutes.
Drain the cauliflower and transfer to an 8×8 baking dish.
Return the pot to the stovetop and set to medium heat. Add the heavy cream, cream cheese, butter, garlic powder, and pepper. Stir until smooth.
Add in half the cheddar cheese and all the Romano cheese.
Stir until the cheese is melted and the sauce is thick.
Pour the sauce over the cauliflower florets in the baking dish.
Stir, mashing gently, until the cheese and cauliflower is mixed.
Spread the remaining cheddar cheese on top.
Bake for 25 minutes or until the cheese is bubbly on top.
Garnish with parsley if desired and serve warm.