In the world of gourmet confections, chocolate truffles take the cake

Chocolate truffles - one of the most luxurious forms of chocolate - have greatly increased in popularity in the United States during the last few years. Shaped in small chocolate balls, they resemble the scarce mushroom truffles of Europe. They are considered a classic French sweetmeat and are also a speciality in northern Italy, where they are often served in fluted chocolate cups.

Available in the US at candy stores, delicatessens, and even department stores, these chocolate specialties are a delicious gift idea or an elegant snack.

Truffles are usually made with chocolate, heavy cream, butter, and cocoa powder, although some recipes call for egg yolks, creme fraiche, and a flavoring such as a nut or fruit syrup, in addition to the other ingredients.

Variations on this basic recipe are endless. There are mint truffles, hazelnut truffles, apricot truffles, orange truffles, and coconut truffles, to name just a few. Truffles can be rolled in cocoa, nuts, or chocolate vermicelli, or dipped in white, semisweet, or dark chocolate.

The price of truffles varies from about $15 to $25 a pound depending on where you buy them and whether they are rolled in cocoa powder or dipped in chocolate.

Rudi's, a national bakery-delicatessen, offers truffles for $18 a pound and in smaller sizes down to a mini box for $3.50, which holds four truffles.

''Truffles are the most popular chocolate,'' says Susan Lennertz, Rudi's marketing director. ''In fact, they're the hottest item on the market right now.'' At Christmastime, she adds, Rudi's just can't keep them in the store. At Easter its ''Truffle Egg,'' which sells for $8.95, also goes quickly.

Truffles are not difficult to make, but when doing your first batch remember that the chocolate mixture must be chilled until very firm so it can be shaped into small balls. If it isn't chilled long enough, it will melt in your hands. Chocolate Truffles 1 cup whipping cream 12 ounces semisweet chocolate, chopped 4 tablespoons unsalted butter, cut in small pieces 1/3 cup cocoa, for dusting

In a medium-size saucepan, heat cream until it simmers along edges. Add chocolate and butter; stir until melted and mixture is smooth.

Remove from heat and cool until lukewarm. Pour onto an ungreased jelly-roll pan, or something similar. Chill in refrigerator or freezer until firm.

Place cocoa powder in a square cake pan and dust hands with cocoa. With a spoon, scoop up a small amount of chocolate. Quickly and gently roll it into a 1 -inch ball. Roll balls in cocoa until lightly coated.

Chill finished truffles on another cookie sheet and chill. Continue procedure.

Store in cool, dry place. Yields about 42 1-inch truffles. Almond Chocolate Truffles 1 cup whipping cream$510 ounces semisweet chocolate, finely chopped 3 tablespoons unsalted butter 1 1/4 cups toasted almonds, coarsely chopped

Powdered cocoa

Heat cream until it simmers. Remove from heat and add chocolate and butter. Whisk until smooth. Add almonds.

Set pan in refrigerator and stir every 10 minutes until mixture begins to thicken. When slightly thick, remove from refrigerator and stir briskly to remove any lumps. Return and chill until hardened.

Shape chocolate into round balls and roll in powdered cocoa.