Potato Leek Soup

Well if it doesn't quite feel like fall outside yet, I can at least cook like it's fall: soup! I bought two gigantic leeks; one went into a frittata and the other languished in the fridge. I finally killed two birds by using up the last of some potatoes and the beautiful giant leek. The preparation took me a little longer than I expected, but I liked the extra veggies in it.

Potato Leek Soup
2 tablespoons olive oil
2 tablespoons butter
2 stalks celery, with leaves, cut into 1/4-inch dice
1 - 2 leeks, white and light green parts
2 shallots, diced
2 cloves garlic, minced
2 pounds potatoes, peeled and cut into 1-inch pieces
8 cups Chicken Stock
2 dried bay leaves
1 sprig fresh rosemary (left whole - not chopped)
2 sprigs fresh flat-leaf parsley
1 cup milk
1/2 cup heavy cream
Salt and freshly ground black pepper
Sharp cheddar and chopped scallions, for garnish

1. Bring potatoes and herbs in chicken stock to a boil in a large saucepan. Reduce to a low simmer.
2. Saute celery, leeks, shallots, and garlic in olive oil and butter in a large skillet. Cook on medium-low heat until very soft but not brown, about 20 minutes.
2. Add leek mixture to potatoes. Cook until potatoes are very tender, about 20 more minutes. Remove bay leaves and rosemary and discard.
3. Puree half of the soup and add back to the pot. Slowly stir in milk and cream. Season with salt and pepper. Serve hot garnished with cheese and scallions.