Steam the potatoes until tender, about 15 minutes.
3 pounds Yukon Gold potatoes
Set the ricer over a large mixing bowl and press the potatoes into the bowl. Season with salt and pepper and set aside.
Kosher salt, Ground white pepper
Adjust oven rack to middle position and set oven to broil. Spray an 8-inch baking dish with nonstick spray.
Beat cream, with the electric mixer on medium speed, to stiff peaks, about 2 minutes.
1¼ cups heavy cream
Using a rubber spatula, gently fold two-thirds of the cream into the riced potatoes until incorporated. Carefully spoon the potatoes into the prepared dish – avoid pressing the potatoes down – we don’t want the potatoes to deflate.
Fold 1¼ cups cheese into the remaining whipped cream and spread the cream/cheese mixture over the potatoes. Sprinkle the top with the remaining ¼ cup cheese.
1½ cups grated Parmesan cheese
Broil until the top is golden, 1-3 minutes. Watch closely and turn the dish when needed to get an even broil.
Remove from the oven and allow potatoes to rest a few minutes before serving.