Instructions: Place the flour, confectioners sugar, granulated sugar, and salt in the bowl of a food processor. Pulse until well-combined. Add the butter, and pulse until coarse crumbs form. Add the lime extract, and pulse just enough to mix. Transfer the dough to a clean work surface, and flatten, forming a disk. Wrap the dough in plastic, and transfer to refrigerator; chill until very firm, at least 2 hours.

Heat oven to 325 degrees. Line a baking sheet with a Silpat non-stick baking mat.

Roll out the dough to an 1/8-inch thickness on a lightly floured surface. Using a 1 3/4-inch fluted cookie cutter, cut the dough into squares. Place squares on the prepared baking sheet, spaced about 1 inch apart. Bake until just golden, 15 to 17 minutes. Transfer to a wire rack to cool completely.

Meanwhile, make the Key Lime Curd: Place sugar, eggs, lime juice, and zest in a medium nonreactive saucepan; set over medium-low heat. Cook, whisking constantly, until mixture begins to thicken and holds the mark of the whisk, 10 to 12 minutes. Remove pan from heat, and whisk in the butter, a piece at a time, until well-combined. Strain mixture through a sieve into a glass bowl. Lay plastic directly on surface to prevent a skin from forming. Chill 3 hours or overnight to set the curd. (Makes 3/4 cup)

To assemble the sandwiches, place 1 teaspoon Key Lime Curd on the underside of half of the cooled squares. Top the curd with the remaining squares to form little sandwiches. Refrigerate until firm, about 20 minutes, and serve.

Makes 24 dessert sandwiches.

Comments: Key limes are smaller than the more familiar Persian limes, and their skins are yellower in color. Native to southern Asia, the key lime was transported to Spain and Portugal by Arab travelers; explorers from these two countries introduced the fruit to North America in the sixteenth century. High in vitamin C, key limes mature in the summer months, but are generally available year-round in larger supermarkets and specialty-food stores.

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