Mousses : These sweet and savory foamy creations will help cooks get through the holiday season.

The word mousse is French for foam. However, in culinary terms, mousse refers to a large category of dishes that have a foam-like, light, smooth texture usually made with a gelatin, egg white or whipped cream base, and can be served chilled or frozen.

The mousse category of dishes is so vast and varied, it is sometimes hard to tell what is or is not a mousse. You can mistake a cold souffle, a pate and a mousseline for mousse and be partly correct. They all have the distinguishing textural features of the mousse, but are categorized differently because of a specific dish, method of cooking or usage particular to them.

But never mind about all that. All you need to remember is that mousses, whatever their form, will help get you by the holiday entertaining season splendidly if you are the cook. That’s because you do them ahead, as did the great French chefs who could never have lived through the elaborate menu productions of the past without the help of mousses.

The wonderful thing about mousses is that they fit into two important segments of a holiday menu--appetizers and desserts.

Mousses are more often than not associated with sweets, and this vast dessert category is unlimited.

One of the most attractive mousses we’ve seen happened to be the work of Annie Rousseau, executive chef of the Hotel Bel Air Sands, who specializes in charlottes (molded cold mousses encased in bread, cake or biscuits). This raspberry mousse is surrounded with ladyfingers, and it can be decorated with whipped cream, fresh, sugared or candied fruit or leaves.

But there is no sweet mousse more unusual in our experience than one made with Swiss chard we sampled at Le Chantecler in the hotel Negresco in Nice, France, this summer.

The mousse was served as a slab on a pool of creme anglaise and raspberry puree. The dessert was made in a loaf pan with a base of the Swiss chard mousse topped with amaretto-flavored mousse. The Swiss chard mousse, we were told, is a specialty of the cuisine of Nice, and desserts made with Swiss chard are found throughout the Mediterranean region.

Other mousse desserts that will help the holiday cook get ahead of the game are also given here. Persimmon mousse made in the persimmon shells can be frozen to have on hand throughout the holiday season if you make several batches.

A white chocolate mousse is served in dark chocolate shells molded out of paper cups. The cups can be prepared weeks ahead and kept frozen until ready to fill with mousse. The mousse also may be frozen in the shells, if desired.

For an easy dessert that you can freeze, you might consider a mousse made from a package of vanilla pudding mix. Adding whipped cream to pudding mixes is a trick learned from chefs, and it works like a dream. You can add whipped cream to any flavor pudding mix and use a complementary sauce to go with it.

In need of fabulous do-ahead appetizers? Try the caviar mousse given here. It’s a recipe from Along Came Mary, a well-known catering firm in town, and it can be prepared a day or two in advance.

If you want to add pizazz to a sit-down holiday dinner menu, try Avocado Mousse served in a small avocado shell with tortilla chips. You can also use the same mousse as a vegetable dip for an informal open-house menu.

The Cucumber Mousse is molded in a large juice can, so it can be served sliced on cucumber slices, crackers or toast rounds. Or it can be served as a log to accompany a cold poached salmon for a holiday buffet.

A Goat Cheese Mousse made with gelatin and whipped cream is molded to serve on grape or citrus leaves with crackers surrounded with grapes for use either as an appetizer or an after-dinner cheese and fruit course. You can, however, serve the mousse as a first course over a beautiful red tomato slice garnished with mint leaves for a holiday sit-down dinner.

A Fish Mousse mixture was turned into a sushi appetizer by rolling it in a sheet of nori (dried seaweed), which can be found at any supermarket or Japanese food store. The roll is then sliced to pass on a tray with cocktails. Or you can form the mousse into egg shapes using a metal spoon for molding the mixture to serve chilled on lettuce or a cutout made of nori for a first course.

Any of the above mousses can be prepared ahead and kept frozen or refrigerated until ready to use. Mousses with a gelatin base should be refrigerated only, since gelatin tends to weep and liquefy unless strengthened with additional gelatin when frozen.

Other technical pointers to watch for when preparing mousses:

If the mousse calls for whipped egg whites, be sure the egg whites are stiff and still shiny, but not dry. The same goes for whipped cream. The whipped cream should be stiff but not dry and should not slip when the bowl is tipped.

When folding either egg whites or whipped cream into the mousse mixture, use a rotating motion with a rubber spatula until the mixture is thoroughly blended but still airy. Do not overbeat. Overhandling will disturb aeration and break down the volume of the product.

You can lightly oil a mold to help ease unmolding. To unmold a stubborn frozen mold, apply hot towels over the surface of the mold to melt the mousse just enough to release it from the sides of the mold. You can also dip the mold quickly into hot water only just until the contents loosen a bit before unmolding.

Keep mousse mixtures covered during refrigerator or freezer storage so they don’t absorb odors of other foods.