MAKES 24 COOKIES

George Lang, a living legend of Manhattan's social circle and a well-known restaurateur, named these treats for Jenny Szemere, who taught him about baking.

FOR THE COOKIES:
1 1⁄2 cups flour, plus more as necessary
1⁄2 lb. cold unsalted butter, cut into bits
1⁄2 cup confectioners' sugar
1⁄2 cup ground walnuts
1⁄4 tsp. salt

FOR THE FILLING:
1⁄4 cup milk
1⁄4 cup sugar
1" piece vanilla bean
3⁄4 cup ground walnuts
2 tbsp. lemon juice
5 tbsp. plus 1 tsp. unsalted butter, softened

1. To prepare the cookies: Put the flour and butter in the bowl of a food processor and pulse until the mixture resembles bread crumbs. Add the confectioners' sugar, walnuts, and salt, and process to mix. If the dough feels too sticky, add more flour, a tablespoon at a time.

2. Flatten the dough into a disk, wrap in plastic wrap, and refrigerate for at least 30 minutes or overnight.

3. Preheat the oven to 375°. Roll out half the dough between two sheets of waxed paper to 1⁄4" thick. With a 1 1⁄2" round cookie cutter, cut out rounds of dough. If the dough becomes too soft to remove the rounds, refrigerate until it is firmer. Transfer the rounds to an ungreased baking sheet and bake 8 to 12 minutes, or until lightly browned around the edges.

4. Cool the cookies on a rack, preferably overnight, so that they will harden slightly.

5. To make the filling: Put the milk, sugar, and vanilla bean in a small saucepan and bring to a boil (do not let the mixture boil over). Reduce the heat, stir in the walnuts and lemon juice, and simmer until thickened. Allow to cool completely. Discard the vanilla bean.

6. When the filling is completely cooled, beat the butter until softened, then stir in the cooled walnut mixture.

7. To assemble: Spread about 2 tsp. of the filling on one cookie and top with another. Repeat with the remaining cookies and filling.