In a large stockpot, melt the butter over medium heat. Add onions and garlic and saute until softened, but not browned. Add the wine and continue cooking until volume is reduced by half. Add the celery root and potatoes. Cover with stock or water by 1-inch. Bring to a boil over high heat, reduce heat to a low simmer, and cook until potatoes are very tender. Using an immersion blender, puree the vegetables until very smooth. Add the cream and return to a simmer. Stir constantly; at this point the soup can burn easily. Season with salt, white pepper, and lemon juice, to taste.

Meanwhile, place the diced potato and celery root in a separate large saucepan and cover with cold water. Season with salt and bring to a simmer. Cook until just tender and then strain and set aside.

Heat the oil in a large skillet over high heat. Add scallops and sear until golden brown on both sides. Remove scallops from skillet and set aside. Ladle some of the soup base into the skillet to deglaze, scrape the bottom of the pan with a wooden spoon, and then scrape back into the large pot of soup. Add the scallops into the soup and keep warm over low heat.

Meanwhile, in another large skillet, melt the butter over medium heat. Add pears and chestnuts and saute until just beginning to brown. Season with nutmeg, to taste. Set aside.

Divide the diced, cooked potato and celery root evenly among soup bowls. Ladle the soup into the bowls and sprinkle with pears, chestnuts, and cheese. Serve with crusty bread or toast.