1. Cut leeks into (roughly) same-sized pieces, about ½ inch to 1 inch thick, depending on diameter. Don't worry about precision — the soup is going to be puréed anyway. We just want the pieces to be of uniform size so that they cook evenly.
2. Peel the potatoes and cut them into pieces about the same size as the leeks.
3. In a heavy-bottomed soup pot, heat the butter over a low-to-medium heat.
4. Add the onion, garlic and leeks and cook for 2-3 minutes or until the onion is slightly translucent, stirring more or less continuously.
5. Add the wine and cook for another minute or two or until the wine seems to have reduced by about half.
6. Add the stock and the potatoes. Increase the heat to medium-high and bring to a boil. Then lower the heat and simmer for 15 minutes or until the potatoes are soft enough that they can easily be pierced with a knife. Don't let them get mushy, though.
7. Remove from heat and purée in a blender, working in batches if necessary.

   Tip: Use care when processing hot items in a blender as the hot steam can sometimes blow the blender lid off. Start on a slow speed with the lid slightly ajar to vent any steam, then seal the lid and increase the blending speed.

8. Return puréed soup to pot and bring to a simmer again, adding more broth or stock to adjust the thickness if necessary.
9. Season to taste with Kosher salt and white pepper.
10. Garnish with a toasted crouton and serve right away.

Makes about 1½ quarts (6 8-oz. servings) of soup.

Optional:

• Stir ¼ cup hot cream into the soup just before serving.