Salad vegetables turn over a new leaf

`And how would you prefer your lettuce cooked, sir?'' is probably not a question any waiter has concerned you with on a recent night out for dinner. Most people know exactly how they like their steak or lamb prepared, and are even particular about their cooked vegetables, but lettuce is usually served raw, tossed in a salad, and unobtrusively dressed with a vinaigrette. No problem, no questions asked, no questions necessary.

Lettuce, like its salad bowl bedfellows, celery and cucumber, is too often thought of as a basic salad ingredient - period. And that's just fine with most of us.

But that's a pity. All three are delicious and far more interesting as cooked vegetables.

Preparing any of these - or other vegetables - in another way changes not only their texture and temperature, but also their character and flavor.

Anyone who has tried baking rather than just boiling beets, for instance, is sure to be a convert. And beets are so often served cooked that people may not know how wonderful they are raw, julienned, and tossed in a salad.

Here are a couple of methods of preparing popular vegetables in uncommon and surprising, wonderful ways.

The first, braised lettuce, is an elegant dish, perfect for a winter buffet. This recipe calls for Romaine lettuce, but most any kind will do, with the exception of perhaps iceberg.

Braising is an excellent and interesting method of cooking other leafy vegetables like endive, escarole, and even celery - which would only require a little longer cooking time.

Just be doubly sure that all the leaves are washed thoroughly to remove any grit at the base of the stems. Braised Romaine Lettuce 2 large heads romaine lettuce 2 slices raw bacon, minced 1/2 cup onion, finely chopped 2 cups chicken stock (approximately) Salt and pepper to taste 1/2 teaspoon thyme or marjoram 3 tablespoons butter

Slice lettuce in half lengthwise right through the core, and in half again. The core will hold each serving of lettuce together. Wash throughly in cold water. In a large pot of boiling salted water, blanch lettuce for 5 minutes. Remove, plunge into cold water, and drain thoroughly. In a heavy baking dish, saut'e bacon and onion. Fold lettuce quarters in half over themselves to form 8 compact packets. Lay the lettuce in baking dish so quarters fit snugly without overlapping. Lettuce should cover the total bottom of dish.

In a saucepan, bring chicken stock to a boil. Add salt, pepper, and herbs to stock and pour over lettuce. Stock should come about halfway up sides of lettuce. Dot with butter, and cover with a sheet of waxed paper, then cover snugly with aluminum foil. Bake in preheated 350-degree F. oven until fork tender, about 1 hour.

Carefully remove lettuce to serving dish and strain braising stock. Hold lettuce covered, in warm oven, while you boil stock to reduce to about one half. Taste and correct seasonings if necessary. Whisk in more butter if you like and spoon stock over lettuce before serving.

Serves 4 to 8. Baked Curried Cucumbers 1 teaspoon butter 3 large cucumbers 4 tablespoons butter, melted 1 tablespoon all-purpose flour 1/8 teaspoon white pepper 1 tablespoon curry powder 1 cup chicken broth

Pre-heat oven to 400 degrees F. Thoroughly grease a baking dish with a teaspoon of butter. Peel cucumbers, halve them lengthwise, scoop out and discard seeds, and cut cucumbers into 1/4-inch slices.

In a blender, add melted butter, flour, pepper, salt, curry powder and chicken broth. Blend until smooth. Pour sauce over cucumbers.

Bake, covered, for 25 minutes. Uncover, and bake an additional 5 to 10 minutes or until sauce has reduced and slightly browned and cucumbers are tender.

Serves from 4 to 6.