In the meantime, heat the butter in a large, heavy pot or Dutch oven. Add the onions, leek, potatoes, and garlic. Cook, stirring, until soft, about 5 minutes. Add the wine and deglaze glaze with white wine, loosening any browned bits in the pot. Add the mixture to the potatoes and continue cooking until the potatoes are just tender. Drain and reserve the cooking liquid. Transfer the potato mixture to a food processor and pulse several times to puree. Transfer the mixture to a large pot. Add the reserved potato broth to the puree and simmer over medium-low heat. The consistency should be soupy. Season with salt and white pepper. Add the cream and stir to blend. Cook for several minutes to heat through. Garnish with the parsley and chives.
Makes 12 to 14 servings