And a simple vinaigrette - a quick blend of oil and vinegar with seasonings - is the freshest and purest of them.

But vinaigrette, that most basic of dressings, the perfect complement to salads, can be so much more. It can serve as a marinade or full-fledged sauce with entrees as well.

At Marigold in West Philadelphia, executive chef Erin O'Shea has come up with some innovative vinaigrettes.

Inspired by the flavor of smoked salmon, which led to thoughts of fried green tomatoes, O'Shea came up with a buttermilk vinaigrette that ties together those two favorite foods on the plate.

"I kept thinking of buttermilk, but I needed some fat to bring out and balance the tang, and that is how the buttermilk vinaigrette came about," O'Shea said.

"It's a great accent to the tomatoes and the smokiness of the salmon." And it works just as well with plain seared salmon fillets, the chef says.

O'Shea's menu of Southern-style foods with contemporary flair includes a unique raisin vinaigrette inspired by her memories of carrot-raisin salad, a dish prevalent at family functions when she was growing up.

"It's a very '70s salad, so I decided to update it," O'Shea said. "And this is where it led me."

After reformulating the salad ingredients as a viniagrette, she also rethought its use, drizzling it over a juicy pork chop and white beans as a finishing sauce. Indeed, vinaigrettes have virtually unlimited seasoning potential - from savory herbs to sweet fruits, with almost every acidic edible eligible to assume the "vinegar" role - in moderation.

Among the most memorable of the genre is the green goddess vinaigrette from food goddess Alice Waters, who created a lighter, brighter version of the original classic dressing at her Chez Panisse using white vinegar and egg yolks instead of mayonnaise.

At Jasper in Downingtown, chef/owner Nick DiFonzo takes pride in creating some of the area's most interesting "house" salads, which come with each entree and change weekly.

One recent salad selection that drew raves from tasters at Jasper featured the chef's champagne pear vinaigrette on field greens, shaved fennel, carrots, walnuts and diced pears. Champagne vinaigrette is one of the dozen or so basics in DiFonzo's repertoire of favored dressings.

Vinaigrettes also get their due in Raising the Salad Bar by Catherine Walthers (Lake Isle Press, $19.95), which offers a wide range of recipes, including the basic lemon and Dijon dressings below.

For all the variety, vinaigrettes start with a pretty much standard three-to-one proportion of oil to vinegar (though some favor a four-to-one ratio) plus salt and pepper to taste. Master that and you can move on to those limitless options "to taste."

Extra-virgin olive oil is considered the ideal base, but flavorful nut oils and neutral canola or grapeseed oil, even toasted sesame oil for an Asian twist, can vary the mix.

Start with a good white or red wine vinegar or a rich balsamic vinegar. From there you can substitute fruit vinegars, rice vinegar, or, stretching the name vinaigrette slightly, freshly squeezed lemon or other citrus juices.

Who doesn't love lemon or raspberry vinaigrette?

Flavorful additions, minced or pureed, include shallots, garlic, anchovies, olives, sun-dried tomatoes, grated citrus zest, diced tomato and such.

A binding agent or emulsifier - a little mustard or egg, or mayonnaise, a dressing already emulsified - will help hold normally incompatible ingredients (think oil and water) in suspension for an hour or so, long enough to serve.

If the mixture does separate, whisk it together again before serving. Blenders, processors and special utensils aside, a fork is all you need.

Then comes the fun part - using a custom vinaigrette not just to moisten greens but also as a light sauce or marinade for fish, seafood, chicken, even beef. Argentine chimichurri is, after all, just a thick herb vinaigrette.

Buttermilk Vinaigrette

Makes about 2 cups, up to 16 servings

1/2 clove garlic, minced

1/4 cup apple cider vinegar

1 cup light buttermilk

2/3 cup real mayonnaise

1/4 cup sour cream