the word chowder refers to the pot (chaudre or cauldron) and begins with bacon or salt pork and aromatic veg like onion and garlic, often celery. potatoes are standard as is fish and or shellfish. Clams are a favorite. Chowder clams are big and tough and need to be ground up. Fish broth/clam broth is normal from the cooking. Then things get regional.
New Englanders add milk (and possibly some thyme and Worcestershire sauce for seasoning. (cream if you can enjoy the calories and want a thicker soup, but milk is traditional)
Folks from lower New York do not add milk and add tomatoes. Specified as Manhattan clam chowder it is very fine but a different taste certainly.
Folks who like it very thick either have to add flour or overcook the potatoes. There are many other variations as well.
To the folks in Maine, the Crown Pilot cracker is essential (still made for them) it is a hard crisp cracker that holds up in soup (and is their thickener). If you can find them, get them!
Other items added : parsley is very nice, a little dash of hot sauce, some white wine, especially if you are not using milk. you can leave out the bacon but it is traditional to chowders.
so a simple recipe:
2 cups potatoes small/med dice
fine dice 1 onion, 2 cloves garlic
pinch or two of dried thyme, 1 tsp of parsley
1 rasher of bacon sliced into lardons (thin strips)
2 cans clams with juice (small)
1 bottle clam juice (8-10 oz)
1 pint whole milk
dash or two of worcestershire sauce and hot sauce
method:
saute bacon until fat is rendered, add onion and saute until soft, add garlic and saute until aromatic (1 min)
add clam juice and potatoes, simmer until softened
add milk and bring to simmer (do not boil)
add seasoning (herbs and dashes of sauces)
when potatoes are fully cooked add clams (already cooked if canned) and warm through, adjust seasoning...should be salty enough. Black pepper optional.
(about 2 servings)