Mexican nixtamal corn is a large-kernel corn (also sold as hominy) that is heartier than regular sweet corn. Look for cooked chestnuts in vacuum packs or cans.
1/2 lb. white posole
1 ham hock
2 bay leaves
3 tbsp. olive oil
1 1/2 cups sliced (1/4-inch) leek whites
3 celery stalks (from heart of celery), sliced
4 garlic cloves, minced
8 3/4 oz. cooked chestnuts
10 oz. white mushrooms, thinly sliced
3 tbsp. sweet sherry
4 cups chicken broth
1 can evaporated milk
Salt and freshly ground white pepper
1. In a large saucepan, combine posole, 6 cups of water, ham hock, and bay leaves. Bring to a boil, then reduce heat to a simmer, and cook until posole is tender, about 1 hour.
2. Meanwhile, in a Dutch oven, heat oil over medium-high heat. Add leek whites, celery, and garlic, stirring until wilted. Stir in chestnuts and mushrooms. Increase heat; when mushrooms start to release their liquid, add sherry. Cook until liquid is reduced to about 2 teaspoons.
3. Add broth and bring to boil; reduce heat and simmer, covered, for 20 minutes. Allow soup to cool for at least 30 minutes, then puree in a blender or food processor. Return pureed soup to Dutch oven. Gently bring soup back to simmer and stir in evaporated milk. Drain posole and add to soup. Discard ham hock and bay leaves and add salt and white pepper to taste.