It is the warmest memory of many a vacation in France: the little Paris restaurant where a white-aproned waiter served a dish glorified on the menu as something homey like blanquette de veau grand-mere, topped off with a still-tepid creme brulee that was just the right mix of crackly and creamy.

The trouble with this picture, it turns out, is that in 21st-century France, chances are high that both the stew and the dessert were assembled and cooked on a production line in a distant suburban factory, that they were quick-frozen and trucked to the restaurant, that they were then microwaved for unsuspecting diners who thought they were sampling traditional French cuisine.

In a survey conducted for the National Union of Hotel, Restaurant and Cafe Operators, a third of French restaurants acknowledged serving such factory-frozen products to clients. Restaurant owners estimated that the real number is substantially higher, as many chefs were embarrassed to admit the shortcuts that, in effect, hoodwink their customers.