MADAM COCOLAT

LUNCHTIME IN PALO ALTO, CALIF.

At a table in a gourmet coffee shop at the stylish Stanford Shopping Center, a 35-year-old woman sips her French-roast coffee and nibbles on a confection she has surreptitiously removed from a distinctive black shopping bag stamped with gold rectangles and the word ''Cocolat.''

The woman, dressed in paisley and wearing pearls, is a financial consultant with a Ph.D. in chemistry from Yale and an M.B.A. from Berkeley. She is making a meal out of her coffee and a $1.75 lemon roulade: a cylinder of pale yellow spongecake filled with delicate lemon cream, dusted with powdered sugar and studded with toasted almonds. She explains why she has chosen the lemon roll over Cocolat's hallmark chocolate truffles, to which she is addicted. ''Chocolate'' she says, ''is far too heavy for lunch.''

Chocolate truffles were virtually unknown in the United States when, in 1973, Alice Medrich started making and selling them from her home in Berkeley. Cocolat, her specialty chocolate company, has flourished in tandem with America's growing taste for upscale foods. Per capita consumption of chocolate has risen from 9 pounds in 1976 to 11.2 pounds last year; luxury chocolates, selling for $12 to $35 a pound, now account for up to 15 percent of total dollar volume - twice as much as a decade ago.

One of Cocolat's seven Bay Area stores is located a few doors down from the coffee shop in Palo Alto. On this day, Alice Medrich, 38 years of age, is paying a visit to her Stanford Shopping Center store. She wears beige pants, a black silk jacket and high-heeled, sling-back, patent leather shoes. Her style, it should be noted, is just like that of her customers. ''It is different from the old days,'' she says, ''when the baker was a whole different social class from the customers, who were carriage trade. Our customers are sophisticated, well-traveled, educated people who work hard and reward themselves with quality treats.''

Behind the shop's clear glass storefront sits a long display counter filled with sculptured confections. Cocolat's top seller is the $18.50 reine de saba, a chocolate torte flavored with almonds and cognac that serves up to 14 people. Next to it is enshrined a tricolor mousse that serves 16: white, mocha and bittersweet chocolate. Its sole adornment is a chocolate version of a wax seal complete with flourish.

A place of honor is reserved for the trays of truffles - rich, dense combinations of chocolate and heavy cream, flavored with liquor, liqueurs, fruits or nuts. There is an ever-changing selection of truffles including cafe au lait (an abstract sculpture of taupe-and-white marble) and milk chocolate sprinkled with toasted almonds (a sleepy hedgehog).