Preparing diamondback terrapin is like cooking lobster but more tedious.

Rinse the terrapins and plunge them into boiling water deep enough to cover. Maintain a low boil for an hour. Run cold water over the terrapins until they are just cool enough to handle. The thin membrane that covers the skin will have come loose and can be easily peeled away.Remove the toenails.

Turn the animal on its back and with kitchen shears sever the bottom shell, or plastron. Save the juices that pool in the top shell, or carapace, when the plastron is pulled free; they will enrich the broth.

The large dark organ that dominates the interior is the savory liver. Free it carefully so as not to rupture the attached green, peashaped bile gland. Cut out the gland and trim away any green-stained portion of the liver. Pick out the eggs and reserve them with the liver. Remove the intestines.

When the head and debris have been cleared away, what you are left with is four legs and associated muscles, which lift easily from the shell. There is rather a small amount of meat, a fair amount of dark fat, and a lot of skin. Keep them separate. Pick carefully, getting everything you can from around and between the little bones. Do not neglect the thin sheets of meat that adhere to the shell. The white muscle is fairly tough and will be chewy in the soup; it helps to sprinkle a little meat tenderizer over it well before cooking.

Rub the liver and eggs through a sieve, and run the skin and fat through a blender until it has the consistency of pudding. Strain and add to the liver and eggs. Now you are ready to go. TERRAPIN SOUP WITH MADEIRA (Yield about 5 quarts) INGREDIENTS: 4 large female terrapins 3 quarts of onions 1 quart of celery 1 quart of carrots 1/2 cup fresh or 1 tablespoon of powdered thyme 1 cup of Madeira wine 6 cans of beer 1 bay leaf

A good vegetable base is necessary because the unalloyed flavor of terrapin is a little rich for the average palate. What follows assumes you are starting with four large females, but can be adjusted for more or less. A small amount of terrapin can be stretched considerably, because it has what in wine is called "a big nose and a long finish." A professional chef who tasted my soup suggested that the carrots made it too sweet and should be cut back.

Add three cans of beer to the blended vegetables and cook well. Add the meat, juice, bay leaf and thyme. Don't skimp on the thyme. Simmer for an hour, adding the other cans of beer if and as needed; what you are aiming for is the consistency of oxtail soup.

Add the sieved liver and eggs freshly ground pepper to taste. Surprisingly little salt will be needed.

Simmer for 15 more minutes. add the cup of Madeira just before serving; its function is to enhance the aroma. Each guest should have a generous glass of Madeira to add to the soup according to taste.

Serving Madeira as a aperitif will prepare the palate for the soup course; one glass in the belly and another in the soup will launch a jolly meal.

Sherry may be substituted for the Madeira, But Madeira is widely available in this area and dollar for dollar is a much better buy. Mais, chacun a son gout. TERRAPIN STEW A LA VIRGINNIE Terrapin soup would have been regarded as heresy by Gilded Agers, whose customary vast starter courses would finish off any modern diner.

Terrapin stew was the dish in those days. Chef Roland Bouyat of Washington has recently developed a variation on the turn-of-the-century stew which he occasionally features as an entree on his weekend menu at The Bread Oven restaurant; it may be the only terrapin dish commercially available.

As in classic method, Bouyat prepares his stew without the use of a blender. To use the recipe given below, follow the directions for the soup recipe to the point where the terrapin has been eviscerated and the eggs and liver reserved. The legs are sectioned at the joints and served whole. Ingredients: 4 large female terrapins 4 large chopped shallots 1 carrot, diced very fine 1 bay leaf 1 teaspoon cornstarch a pinch of thyme 1 quart of whipping cream 4 ounces of butter 3 ounces of green peppercorns 1 cup of dry white wine 2 ounces of Cognac or brandy 2 ounces of good sherry

In a large saucepan heat the butter well and add the preboiled terrapin (white meat and joint legs along with sections of skin and fat). Salt lightly and fry briefly. Add sliced shallots and carrots and the green peppercorns. Saute for a few more minutes.

Remove the pan from the stove and add the Cognac or brandy; flame. Then add the white wine and cream. Heat gently until reduced by half. Slice liver and eggs thin and add to pot. Thicken sauce with cornstarch dissolved in half the sherry. Add the rest of the sherry just before serving. d

Serve with rice and vegetables of choice. Bon apetit!