1. Cut leeks in half lengthwise. Rinse well under cold running water to remove any grit. Thinly slice crosswise; set aside.

2. Cut endives in half lengthwise, and cut out and discard the cores. Thinly slice crosswise; set aside.

3. Peel potatoes, and cut into 1/2-inch pieces. Set aside in a bowl of cold water.

4. Heat butter in a saucepan over medium heat. Add leeks; cook until they start to soften, about 3 minutes. Drain potatoes well; add to pot along with sliced endive. Cook until vegetables begin to soften, about 10 minutes; do not let brown.

5. Add wine and stock, and bring to a gentle simmer. Cook until vegetables are very tender, about 1 hour. Cool slightly.

6. Transfer soup in batches to a blender (fill no more than halfway), or pass it through a food mill. Return to a clean saucepan; stir in cream. Bring to a simmer; remove from heat. Season with salt, pepper, and nutmeg. Garnish with endive.