How to Make It
In a medium saucepan, cover the potato chunks with the cream and milk. Season lightly with salt and pepper and bring to a boil. Partially cover the saucepan and simmer until tender, about 15 minutes.
Meanwhile, in a large soup pot, melt the butter in the oil. Add the onion, celery, leek and thyme and cook over moderate heat until softened, about 4 minutes. Add the wine and boil until nearly evaporated, about 5 minutes. Add the chicken stock and season very lightly with salt.
Using a slotted spoon, transfer half of the cooked potatoes to a bowl. Transfer the remaining potatoes and all of the liquid to a blender and puree until very smooth. Add the potato chunks, the pureed potatoes and the corn to the soup pot and simmer just until the corn is tender, about 4 minutes. Stir in the whitefish. Add the dill and parsley and season with Tabasco. Serve hot.