If you’d like a deeper golden top, turn the broiler on high for 1–2 minutes at the end of baking, watching closely so the cheese doesn’t burn.
Remove the dish from the oven and let the asparagus rest for 5 minutes. The sauce will thicken slightly as it stands, turning silky and spoonable.
Sprinkle with chopped fresh parsley or chives, if you like, and serve the asparagus straight from the glass casserole dish, spooning some of the creamy garlic Parmesan sauce over each serving.
If you like a little extra color and flavor, tuck a few thin slices of red bell pepper or a handful of halved cherry tomatoes in among the asparagus spears before pouring on the cream mixture, keeping in mind this adds a touch of natural sweetness. For even more richness, swap half of the Parmesan for grated Asiago or Romano. You can also add a pinch of crushed red pepper flakes to the cream mixture for a gentle heat, or a small squeeze of lemon juice at the end for brightness. If your family prefers a thicker, almost gratin-style sauce, stir an extra 1/4 cup Parmesan into the cream mixture before baking and let it stand a couple of extra minutes after it comes out of the oven. To stretch the dish for a larger group without adding many carbs, mix in a few blanched green beans or a handful of sliced mushrooms with the asparagus. Leftovers reheat nicely in a low oven or gently on the stovetop over low heat; just cover the dish with foil and warm until the sauce loosens and the asparagus is heated through.
