From Great Meals from the Northwest, Judie Geise, 1978 (originally printed in 1945)
2 pounds mussels, cleaned
1 tablespoon butter
3/4 cup salt pork, blanched and diced
2 leeks, including 2 inches of the green top, cleaned and finely chopped
3/4 cup celery diced
1-1/2 cups potatoes diced
pinch cayenne pepper
1/4 teaspoon powdered saffron or turmeric
1/2 teaspoon salt
3-1/2 cups milk
1/2 pint heavy cream
3 tablespoons parsley minced
Steam the mussels for no longer than five minutes, extract the meat, chop coarsely, and reserve
Reduce the cooking liquid over high heat to 1 cup and reserve it, too
Melt the butter in a 5 quart heavy pot, add the salt pork and saute until crisp and golden brown. Remove the pork bits, drain on paper towels and reserve.
In the rendered fat left int he pot, saute the leeks, celery and potatoes over high heat for five minutes. Sprinkle the vegetables with the cayenne, saffron or turmeric, and salt; add the reserved broth, bring to a boil and cook for a few minutes.
Remove the pot from the heat and add the milk and heavy cream, stirring well. Over low heat cook the chowder for about 1/2 hour until the potatoes are soft; then add the reserved mussels and pork bits and simmer for a few minutes to warm the shellfish and blend the flavors.
Serve immediately, topping each bowl with parsley. If the chowder is to be reheated, do not boil or it will curdle.
Note: we had an amazing mussel chowder in New Zealand that seems like a similar recipe, with the addition of carrots to the mix.
