1In a large pot over medium heat, melt butter until foaming. Add olive oil, shallots, and pear, season well with salt and ground white pepper, and cook, stirring occasionally, until tender, about 5 minutes.
2Add celery and thyme, season with more salt and pepper, and sweat until most of the liquid has evaporated and the celery has just started to soften, about 12 minutes.
3Add broth and water, increase heat to high, and bring to a boil. Once boiling, reduce heat to medium and simmer until celery is tender, about 10 minutes.
4Using a blender, purée soup in batches until smooth. Return soup to the stove to reheat. Season well with salt and pepper.
For the garnish (optional):
1Heat olive oil in a small frying pan until bubbling or about 325°F to 350°F.
2Add half of the shallots and fry until golden. Remove to a plate lined with paper towels, season with salt, and repeat with remaining shallots.
3Serve soup topped with fried shallots.
Beverage pairing: The delicate and fine flavors here suggest a Riesling, but to reinforce the rare and green flavor of celery, try going to a comparable but different wine, Grüner Veltliner from Austria. A light style with a little characteristic pepper fits the bill: 2006 Schloss Gobelsburg Gobelsburger.