How to Make It
Preheat the oven to 350°. In a medium saucepan, combine the Sauternes, sugar, cinnamon stick, caraway, a pinch of salt and 2 3/4 cups of water. Bring just to a boil, stirring to dissolve the sugar. Add the Asian pear halves, cover and poach over moderately low heat, turning occasionally, until barely tender, 25 to 30 minutes. Remove from the heat and let cool completely. Core the pears and cut them into 12 wedges each. Return the pear wedges to the poaching liquid.
Meanwhile, on a rimmed baking sheet, toss the bread cubes with the olive oil and season with salt. Bake for about 10 minutes, until just crisp; let cool.
In a large saucepan, melt the butter. Add the napa cabbage and a generous pinch of salt and cook over moderately high heat, stirring occasionally, until wilted, 12 minutes. Add the vegetable stock and 6 cups of water and bring to a boil. Simmer over moderately high heat, stirring occasionally, until the cabbage is very tender, 10 to 12 minutes.
Working in batches, puree the cabbage soup with the crème fraîche in a blender until smooth. Strain the soup through a fine sieve into a clean saucepan. Bring the soup just to a boil and simmer over moderate heat, stirring often, until reduced to 8 cups, about 7 minutes. Season the soup with salt.
Ladle the soup into shallow bowls. Using a slotted spoon, add the poached pears to the bowls. (The poached pear liquid can be served with sparkling water as a spritzer.) Garnish with the pumpernickel croutons, julienned cabbage and diced Gruyère, drizzle with mustard-seed oil and serve.
Pungent mustard-seed oil, such as the Australian-made one from Naturally from Nature, is available at specialty food stores and from farawayfoods.com.