New England Clam Chowder - The Fish Market

30-plus ounces canned chopped clams (see note)
4 tablespoons butter, divided use
1 cup chopped onion
1 cup chopped celery
1 garlic clove, minced
3 cups diced raw peeled potatoes
1 teaspoon celery salt
1/2 teaspoon thyme
1/4 teaspoon ground white pepper
2 tablespoons flour
Salt, to taste
4 cups half-and-half

Drain clams, reserve and measure the clam liquid, add water if amount is less than 4 cups.
Over medium heat melt 2 tablespoons butter, add onion, celery and garlic, sauté for 5 minutes.
Add potatoes, celery salt, thyme, pepper and clam liquid, simmer until potatoes are tender.
Make a roux by melting remaining butter and mix in flour, cook 1 minute.
Stir roux into potato mixture, cook 1 minute more.
Add salt, as necessary to taste.
Add clams and half-and-half and heat through, but do not boil.
NOTE: Use three 10 1/2-ounce cans or five 6 1/2-ounce cans.

Makes about 12 cups