A great dessert is perhaps the most difficult dish to create. I could spend days substantiating that opinion but, most simply stated, sugar provides the foundation for hundreds of really good desserts, and "really good" is quite often good enough.

Sifting slowly through the thousand desserts in my memory I find only a few truly great desserts. One was a Key Lime Pie in Coconut Grove. Another was an elegantly exotic, dreamily sensuous tart in Paris. The most recent addition I found on one of my rare visits to Washington: Geppetto's Ricotta Cheese Pie.

"Do the cheese pie," a friend whispered when she introduced me to Geppetto's restaurant, that Georgetown reminder of the high-strung wooden boy whose nose grows every time he tells a lie.

Cheese pie? This couldn't be how Washingtonians refer to pizza."

"Just do it."

Cheese pie, as she called the Dolce de Ricotta, turned out to be a simple but stunning combination of ricotta cheese, chocolate chips, toasted sliced almonds, almond extract, sugar and whipped cream . . . chilled overnight in its graham cracker crumb crust. Forget pizza.

The really remarkable thing about this dessert is that it's calorie-free.

"What!?" you say. "With a list of ingredients that could get anyone committed to a life term on a fat farm -- not to mention the whole pint of whipped cream -- you're crazy!"

No! I'm telling the truth . . . honest. Oops; my nose just grew 2 1/2 feet. Oh, well, at least it is worth it.

GEPPETTO'S RICOTTA CHEESE PIE (12 to 16 servings)

Crust: 1 1/4 cups graham cracker crumbs 1/4 cup sugar 6 tablespoons melted butter

Filling: 2 1/2 cups (1 1/4 pounds) ricotta cheese 3/4 cup sugar 1 cup toasted sliced almonds 1/2 cup semi-sweet chocolate chips, frozen 1 pint whipping cream 1 teaspoon almond extract

Garnish: 1/4 cup toasted sliced almonds

"This is a very simple recipe," says Alvin Snodgrass, Geppetto's chef. "If ever a problem comes up, it's always with the crust. Make sure it's cooked well, otherwise it falls apart. When you bake it in the oven, make sure it's solid. In other words . . . the sugar must break down and crystallize with the butter to hold it together. If it's underbaked, well, when you cut out a piece of pie, the crust will be laying on the bottom and the ricotta filling will come out by itself."

To make the crust, combine crust ingredients and press the dough firmly and evenly against the bottom and sides of a 9-inch pie plate. Bake for 10 to 12 minutes at 350 degrees, remove, and let stand until completely cool.

"Another consideration," Snodgrass continues, "is the ricotta cheese. It needs to be a dry cheese. Some ricottas seem to be wetter than others, so be sure to drain or, if need be, press wet ricotta in a strainer. If the liquid gets mixed with the whipping cream as it's folded in, it tends to break down the whipping cream.

"The chocolate chips must be frozen solid before you begin working with them. Just before we fold in the whipped cream we take them out of the freezer and run them through a food processor. When the bits are removed from the processor, we take just the bits and not a speck of dust. If you use the dust, that will kill the contrast in the pie -- of the white ricotta, whipping cream, ground almonds and the bits. With the dust included, you'll just have a chocolate-covered pie.

"We toast the almonds in the oven," Snodgrass adds. "Then we let them cool down and then run them through the processor. You want to get sort of a grapenut texture. That's really all the instructions, or secrets, there are; it's simple!"

To make the filling, beat the cheese and sugar together in a large mixing bowl. Stir in the ground nuts. In another bowl, partially whip the cream. Add the almond extract and continue beating until the cream holds peaks. Then you do the chocolate (because it should be frozen). Run the chips through the processor or blender and then mix the bits into the cheese. Fold in the whipped cream, but "do not overfold," Snodgrass warns, "or it will go flat."

Gently spoon the filling into the pie shell and refrigerate at least several hours or, preferably, overnight. Before serving, sprinkle on a handful of sliced toasted almonds. (If you really want to drive people insane, put on a thin coat of whipped cream before sprinkling on the nuts.)