This recipe is among those that reach a new level when made with sea salt. Cut them with a turkey-shaped cookie cutter and serve on Thanksgiving!
3/4 cup pecans (3 oz), toasted and cooled, plus about 32 pecan halves (3 oz)
2/3 cup plus 2 tablespoons confectioners sugar
1 1/4 cups all-purpose flour
1/2 teaspoon sea salt
1/4 teaspoon baking powder
1 stick (1/2 cup) unsalted butter, softened
1/2 teaspoon vanilla 1 large egg, separated
Preheat oven to 325°F. Pulse toasted pecans with 2 tablespoons confectioners sugar in a food processor until finely ground. Whisk together flour, salt, and baking powder in a bowl.
Beat together butter, remaining 2/3 cup confectioners sugar, and vanilla in a bowl with an electric mixer at high speed until pale and fluffy, about 3 minutes. Add egg yolk and beat well. Add flour and ground-pecan mixture and mix at low speed until just combined, 30 seconds to 1 minute. (Dough will be crumbly but will hold together when squeezed.)
Halve dough and roll out 1 half between 2 sheets of wax paper until 1/4 inch thick (about a 9-inch round). Cut out as many as possible with cookie cutter and arrange about 2 inches apart on buttered large baking sheets, reserving scraps. Roll out and cut remaining dough in same manner. Gather scraps, then reroll and cut in same manner.
Beat egg white until frothy, then brush tops of cookies lightly with egg white.
Bake cookies in middle of oven until tops are pale golden, 15 to 20 minutes. Cool cookies on sheets on racks 2 minutes, then transfer to racks to cool completely.