4ouncesreduced-fat cream cheeseat room temperature
1/4cupnonfat plain Greek yogurt
2/3cupfreshly grated Gruyereor similar melty, nutty, alpine-style cheese, divided
1/4cupfinely grated Parmesan cheesedivided
Place racks in the upper and lower thirds of your oven and preheat to 425 degrees F. Lightly coat a wide 3-quart (9x13) casserole dish, with nonstick spray, and line a rimmed baking sheet with parchment paper.
In a large bowl, toss the cauliflower florets with olive oil, garlic powder, salt, pepper, and nutmeg.
Transfer the cauliflower to the prepared casserole dish and spread it into an even layer. Keep the bowl handy. Roast cauliflower on the lower rack for 30 minutes, until the florets are tender and begin to brown.
Meanwhile, arrange the bacon strips in a single layer on the prepared foil-lined baking sheet. Bake on the upper rack until crisp, about 10 to 15 minutes.
Remove the bacon and cauliflower from the oven. Stir the cauliflower, spread it back into an even layer, and place it on the upper rack to continue cooking until the end of its baking time.
Transfer the bacon to a paper-towel-lined plate and lightly pat dry. Once cool enough to handle, roughly chop or crumble the bacon into small pieces.
In the same bowl that you used to toss the cauliflower, beat together the cream cheese and Greek yogurt until combined. Stir in 1/3 cup Gruyere cheese, 2 tablespoons of Parmesan cheese, and half of the chopped bacon.
Remove the roasted cauliflower from the oven and dollop the cream cheese mixture over the top. Sprinkle with the remaining 1/3 cup of Gruyere and 2 tablespoons of Parmesan.
Return the pan to the upper third of the oven and bake until the cheese is melted and gooey, about 5 to 7 minutes. Turn the oven to broil. Broil the casserole until golden on top, 1 to 3 minutes. Do not walk away, and watch carefully to make sure the cheese does not burn.
Remove from the oven and sprinkle with fresh chives and remaining bacon. Serve hot.
TO STORE: Leftovers may be stored in the refrigerator for up to 3 days.
TO FREEZE: Baked cauliflower casserole may be kept frozen for up to 3 months. Defrost overnight in the fridge before warming.
TO REHEAT: Warm the cauliflower casserole in an oven preheated to 350 degrees F until steaming and heated through.
TO MAKE AHEAD: The cauliflower can be roasted 1 day in advance. Store in an airtight container in the refrigerator. The cream cheese mixture can be prepared 1 day in advance and stored in the refrigerator. When ready to cook, warm the cauliflower in the baking dish in a 350-degree F oven until hot. Let the cream cheese mixture come to room temperature. Increase the oven temperature to 425 degrees F, then dollop on the cream cheese and bake as directed.
TO DOUBLE: This recipe is easy to scale! Feel free to double it (bake in two separate 9x13-inch pans) or halve it and bake in a 1 1/2-quart casserole or gratin dish.