Preheat the oven to 400 degrees . Mix the salt, egg whites and five-spice powder with a fork. Place a scoop of the salt mixture on a foil-lined baking sheet. Set the rutabaga on top; pack on the remaining salt mixture to encase the vegetable completely.
Roast the rutabaga until tender when pierced with a knife through the crust, about 2 hours.
In a small skillet, bring the cream, ginger and garlic to a boil. Reduce the heat to low, cover and cook until thickened slightly, about 10 minutes. Discard the ginger and garlic. Stir in the butter and cilantro; season with salt and pepper.
Using a mallet or a wooden spoon, crack the salt crust; discard. Quarter the rutabaga, then slice each wedge into 1/2-inch-thick pieces. Serve topped with the sauce.