about 3 pounds corn, peanut, or other mild vegetable oil, NOT olive. colored rind only, no pith. Steamer (or soft-shell) clams are naturally tender enough to be cooked, chilled, and sauced for a vivid and satisfying first course. The sauce here is no kin whatsoever to the ketchupy stuff that too often swamps cold seafood; it's a good bet with cold shrimp or crabmeat, too. Small quahogs (on the East Coast) or Manila or other local hard clams (West Coast) may be substituted for steamers. Because their shelled-out meats are firmer and their necks needn't be skinned, they tend to be neater morsels than the raggedy soft-shells, but steamers hold the edge from flavor. Be sure to steam hard clams just until they begin to open; they can toughen in a flash if over-cooked. Boil half an inch of water in a large pot. Add the well-scrubbed clams (see STORING & CLEANING CLAMS), cover, and bring to a boil over high heat. Uncover (to prevent boiling over) and cook, shaking the pot or stirring the shellfish whenever the foam boils high, for 2 or 3 minutes, or just until all the clams have opened. Pour the potful into a collander set over a big bowl; reserve the broth. When the clams have cooled, shuck them, pulling off and discarding the rubbery ring of membrane encircling the bodies as well as the loose, dark skin covering the "neck," or siphon. Place in a big bowl. Strain the broth onto the clams through cheesecloth in a sieve; stop pouring before any sand appears. Stir and swish the clams through the broth to further desand them (some grains always survive the earlier steps). Lift out the clams with a slotted spoon and set them aside. Let the broth settle, strain it again, and repeat the clam rinsing and draining, twice if it seems a good idea. Chill the clams. Refrigerate or freeze the broth for a future chowder or sauce. No more than 3 hours before serving, drain the clams again and fold them into about half the mayonnaise. Refrigerate. To serve, divide the sauced clams among seafood cocktail glasses or small glass bowls. Top with more mayonnaise; garnish with a leaf or two of green stuff -parsley, coriander, watercress, or baby lettuce. LIME, CHIVE, & MUSTARD MAYONNAISE: Whisk together the egg yolk, lime juice, and mustard. Whisking hard, begin adding oil a few drops at a time, beating in each addition completely before adding more. After the mixture has thickened, add the remaining oil in a thin stream while beating rapidly. Season with salt, pepper, chives, lime zes, and Tabasco. Taste carefully; the mayonnaise should be highly seasoned, so add more lime juice, mustard, pepper, and/or Tabasco if needed, but be cautious about the salt -the clams will supply enough brininess for most tastes. Refrigerate until needed. STORING & CLEANING CLAMS: Store fresh clams in the refrigerator with a light covering, not airtight. Clean them as close to cooking time as possible. To clean, scrub the shells under the running cold tap with a vegetable or potato brush; give special attention to the hinges. Cover with fresh water and soak for an hour or so, stirring them about once or twice. Lift them out of the soaking water to leave behind the sand they will have shed. -from MRS. WITTY'S HOME-STYLE MENU COOKBOOK, by Helen Witty