2 cups (about 5 1/2 ounces) whole pecans
2 1/2 cups all-purpose flour
1/2 teaspoon baking powder
1 1/2 teaspoon salt
1 cup (2 sticks) unsalted butter at room temperature
1 1/4 cups confectioners' sugar, sifted
1 large egg
2 teaspoons vanilla extract
1. Toast the pecans by spreading them out on a baking sheet and cooking at 350 degrees until fragrant, about 10 minutes. Cool slightly, then process pecans in a food processor until finely ground; do not process them into a paste. Set aside.
2. In a small bowl, whisk together flour, baking powder and salt, and set aside. Put butter and confectioners' sugar in the bowl of an electric mixer and mix on medium until pale and fluffy, about 2 minutes. Add egg and vanilla, and mix well until combined. Reduce speed to low and add flour mixture and half of the ground pecans, mixing until just combined. Wrap dough in plastic; refrigerate about 30 minutes.
3. Preheat oven to 350 degrees. Roll tablespoon-size pieces of dough into 2-inch logs. Roll logs in remaining ground pecans. Place on baking sheets lined with parchment paper, spacing them about 1 inch apart. Bake cookies, rotating sheets halfway through, until pale golden and slightly cracked, 14 to 15 minutes. Transfer logs to wire racks to cool. Makes about 40 cookies.