In a medium saucepan, combine the potatoes, water, and 1/2 teaspoon of the salt and bring to a boil over high heat. Reduce the heat to medium-high and cook until tender, for 8 to 10 minutes. Remove from the heat and drain in a colander.
Place the potatoes back in the pot over medium heat, add the cream, roasted garlic, the remaining 1 1/2 teaspoons salt, and the white pepper and mash vigorously with a potato masher until fairly smooth, for about 4 minutes. Whisk in the butter and remove from the heat. Serve immediately.
Yield: about 2 1/2 cups
Note: Preheat the oven to 400?F. Combine 24 peeled shallots and /or garlic cloves with 1 teaspoon olive oil, 2 teaspoons salt, and 5 turns freshly ground black pepper on a sheet of aluminum foil. Fold the edges of the foil together to form a bag and roast until tender, for about 40 minutes. Use immediately, or refrigerate in a little olive oil in an airtight container for 2 or 3 days.