-
Preheat oven to 425ºF.
-
Toss the quartered shallots with the olive oil, balsamic vinegar and thyme in a small baking dish. Season with salt and pepper. Bake for 40-50 minutes, stirring every 15 minutes or so, until the shallots are tender and beginning to brown. Set aside.
-
While the shallots are roasting, start the puree. Combine the water, milk and salt in a large saucepan set over high heat. Bring to a boil, then add the celery root and potato; return to a boil. Reduce heat to medium and simmer until the vegetables are tender, about 30 minutes. Drain.
-
Combine the celery root, potatoes and butter in a food processor and puree until smooth. Season to taste with salt and white pepper.
-
Transfer the celery root puree to a serving bowl and form a well in the middle; spoon the balsamic roasted shallots into the well and serve.