I'm in my third supermarket of the morning, searching for a box of cookies. Not just any cookies. I'm looking for a specific kind of cookie, one that is crucial for one of the simplest, creamiest, no-bake desserts that a summer cook could want.

The cookies are Nabisco Famous Chocolate Wafers. They are thin, round and a dark chocolatey brown that's almost black. They're crisp and not too sweet -- sort of like a svelte Oreo, but without the filling.

They are also a pain in the neck to find.

The cookies have been around since 1924, according to Nabisco's archives. Uneeda Bakers, a long-ago division of the National Biscuit Company (now just known as Nabisco), originally offered the simple chocolate wafers as well as ginger and sugar ones. Those two flavors eventually were discontinued, but the chocolate ones have endured. Barely. Although many ice cream pie and cheesecake recipes calling for a chocolate crumb crust will recommend them, the wafers have become harder to come by. They're not a big seller, unfortunately, and many supermarkets have stopped carrying them.

One wafer fan -- Portland law professor Jack Bogdanski, who until recently had a popular web log called Jack Bog's Blog -- posted this sardonic "consumer quiz" in February: "Which is easier to buy in Portland? A. Heroin, or B. Nabisco Famous Chocolate Wafers?"

Bogdanski went on to complain that "it's much harder to find Nabisco Famous Chocolate Wafers than it is to find heroin. Not only can't you find them on the shelves of supermarkets, they're also not even mentioned on the Nabisco snack Web site."

"They're as scarce as hens' teeth, I tell ya," he grumbled in his blog.

I'm looking for them because I want to make a dessert that my mother used to make. It's a refrigerator cake that some call Zebra Cake and others just call icebox cake. It's absurdly simple -- just sweetened whipped cream and the chocolate wafers. The recipe is on the yellow Famous Wafer box, and there's a picture of the dessert as well.

As a child, I would watch my mother make this cake for company. First, she'd whip the cream (I'd get to lick the beater afterward, another reason I liked this dessert so much). Then she'd dab some whipped cream on each cookie and stand them on edge, like a row of dominoes, on a serving tray.

When they were all lined up, she would smear the rest of the whipped cream over the cookies to make a long, white log. The log would go into the refrigerator for several hours (sometimes overnight). When it was time for dessert, she would dust the cake with some cocoa powder or grated chocolate. Then she would slice it, on the diagonal, revealing zebra-stripe layers of white cream and dark chocolate. To a child, this seemed like magic. How did a rather messy log of cookies and cream turn into this yummy layered dessert?

In searching for the cookies to make the dessert myself, I also wondered just how long the recipe had been around. In many articles and cookbooks, including the upcoming "King Arthur Flour Cookie Companion" (November 2004), the dessert is described as "dating back to the '50s." But my mother told me that my grandmother had made it for the dinner parties she threw in the '30s.

Food historian Laura Shapiro, author of "Something From the Oven: Reinventing Dinner in 1950s America," remembers the cake from the '50s, but she notes that many of the foods that were popular after World War II actually had their roots two decades earlier. "It may have blossomed in cookbooks of the '50s," Shapiro says, but she suspected it was older.

In fact, this so-called '50s dessert is at least 75 years old.

In Nabisco's archives is a 1929 ad for the chocolate wafers. The copy suggests layering the wafers with whipped cream and refrigerating them overnight for an easy, elegant dessert. By 1930, the recipe was printed on each tin of the chocolate wafers.

"And there is a story behind this," says author Stephen Schmidt, who is working on an in-depth history of American desserts.

This icebox cake, he says, is part of a much larger group of 1930s refrigerated desserts that have their roots in the late 1800s.

"These refrigerator desserts were quicker, easier ways of making charlottes, a chilled dessert that was hugely fashionable from about 1870 to World War I," says Schmidt. A charlotte was made by lining a pan or decorative mold with ladyfingers or sponge cake and filling it with a cooked custard or flavored whipped cream that had been firmed up with gelatin.

At the same time, he says, thin chocolate cookies, always called wafers, had been very fashionable since the 1880s and early 1890s. "A number of them are in the first Fannie Farmer cookbook and other books of that vintage," says Schmidt. It's not surprising that wafers were among the first commercial cookies.

As food companies began to grow in the 1920s, they looked for better ways to market their products. Complex desserts like the charlotte were reconfigured, says Schmidt, "to make them more accessible to middle-class housewives" and, in Nabisco's case, to help sell cookies. Unlike the more complicated charlottes, the icebox cake was the essence of speed and simplicity.

Schmidt associates the icebox cake with his grandmother, who made it in the '30s and '40s, and his mother, who made it when he was growing up in the '60s.

"People are rediscovering it," he says. "They think it's delicious and so completely simple. It's not garish or over the top."

Versions of the dessert have appeared recently in Everyday Food magazine, where the whipped cream was flavored with a little mint extract, and in Fine Cooking magazine, where it was given a more sophisticated twist with coffee and hazelnuts. On the Food Network, chef Sara Moulton has demonstrated a version made with fresh raspberries.

So where can you find the Famous Chocolate Wafers? I trolled the cookie aisles at four supermarkets before I hit pay dirt at a Giant near my home.

As I walked down the aisle, I ignored the eye-level shelves where the most popular, heavily advertised cookies sat. Instead, I stood on tiptoe, searching the top shelf where the less flashy cookies were stashed. And that's when I saw them. The narrow, bright yellow box with the clear cellophane-wrapped top. The tightly packed row of dark chocolate wafers just visible inside. I reached up. There were two boxes left. Just enough, I thought, for one cake and lots of wafers left over for snacking.