If you are new to the Midwest and friends invite you to a fish boil, your first reaction may be dismay. You may feel homesick for fried clams and the pristine broiled-with-lemon. You may think snide thoughts about regions that offer five kinds of sausage for every fish you can find in the supermarket.

Overcoming ignorance, it is easy to salute a superior fish dish. Fish boils are neither a loathesome skin condition nor a poor alternative to poaching. As prepared in northern Michigan, the fish boil is a delightful variation on the chowder which somehow manages to combine the spectacle of the Hawaiian pig roast with the hominess of the church supper.

Fish boils originated in Door County, where they are ubiquitous as Burger Kings on the Beltway. A quick glance at a map suggests why they evolved. Door County lies between Green Bay and Lake Michigan, home of the Great Lakes whitefish. It was settled by Scandinavians and Icelanders, who are champions of the plain-and-hearty school of fish cookery. According to local sources, the fish boil offered an obvious solution to the problem of feeding cold and hungry fishermen quickly. Responding to a universal chowder-making instinct, the cooks on commercial fishing boats simply boiled huge quantities of potatoes and onions with the day's catch.

The contemporary version served in Door County restaurants differs only in the setting. Preparation still provides half the fun and all the drama. It begins at twilight, when the diners gather outdoors around an enormous caldron of water. (Reservations must be made well in advance for each boil, which serves about 50.) The boilmaster builds a hot wood fire under the caldron, leaning extra logs against it to concentrate the heat underneath. When the water reaches a steaming, rolling boil, the boilmaster adds potatoes, onions, and whitefish in turn in separate steamer baskets.

The secret ingredients in this brew are salt and fuel oil. Salt raises the water temperature and allegedly prevents the fish from shredding. The quart of salt the boilmaster adds to the caldron seems to have no ill effects on flavor or texture.

The fuel oil (no. 1 fuel or kerosene, never gasoline) goes under the pot 10 minutes after the fish is added. The boilmaster ceremoniously circles the caldron and cautions the crowd to move back. Then he pushes away the extra logs and quickly dowses the fire with fuel oil. The flames roar 20 feet into the air, instantly making the brew boil over. This neatly removes the scum accumulated in cooking, and quenches the fire. The boilmaster then runs to the caldron with his assistants, lifts the steamer baskets out with long poles, and races them indoors, followed closely by the diners.

Indoors the mood is strictly church supper, with cafeteria service, paper plates, and friendliness all around. The traditional accompaniments to the meal are in keeping with this atmosphere: creamy coleslaw, homemade breads, and cherry pie. Oddly enough, at the fish boils I visited, the breads weren't as fresh as the fish and the pie wasn't as fresh as the bread. Nobody seems to mind, and anyway the fish is the real star of the show -- as sweet, tender, and delicate as any I've ever eaten on any coast. The generous ladle of melted butter poured over the boiled ingredients removed the last trace of longing for the coast of Maine.

If you can't make it to Door County, you can still enjoy a modified version of the fish boil at home. It's a particularly good choice for a large crowd because the preparation is as easy as the results are delicious. You must have a large container (10- to 12-quart stock pot) and use the freshest fish you can find. Tradition calls for white non-oily fish cut in 1/4-inch steaks, but in a recent testing, bass steaks and monkfish fillets worked just fine. As you might imagine, this is a very monochromatic meal, so you might want to bend tradition by serving a carrot salad and garnishing with lots of parsley. DOOR COUNTY FISH BOIL (6 to 8 servings) 6 to 8 unpared potatoes 1/2 cup salt, or to taste 6 to 8 medium onions, peeled and stuck with fork to keep them from coming apart 12 to 14 fish steaks 1 cup melted butter Lemon wedges Parsley for garnish

Place potatoes in a 10- to 12-quart stock pot and cover with enough water to fill 3/4 full. Heat to boiling. Add 1/4 cup of salt and the onions; heat to rolling boil and boil vigorously 15 minutes.

Carefully lower fish into boiling water in wire basket. Add 1/4 cup salt (not directly onto fish) and cook uncovered until fish just flakes when tested (8 to 12 minutes). Skim scum off the top with spoon, then drain fish and vegetables. Serve with a dish of melted butter and lemon. Garnish fish with parsley.

Timing is critical to the outcome, as nothing tastes good if it's been boiled too long. But if you watch the clock closely and pass the butter liberally, I guarantee you'll wish you'd cooked more.