1. Weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and next 5 ingredients (through salt) in a food processor; pulse until walnuts are finely ground. Add butter; pulse just until mixture resembles coarse meal. Add 2 tablespoons ice water; pulse until dough is moist. Scrape mixture onto a work surface; knead briefly, just until dough comes together (mixture will seem crumbly). Press dough into a 12-inch log on a sheet of plastic wrap. Cover and place in freezer 1 hour or until firm.
2. Preheat oven to 350°.
3. Cut dough crosswise into 16 equal portions; roll each portion into a ball. Working with 1 ball at a time (cover remaining balls to prevent drying), place ball on a baking sheet coated with cooking spray. Using the bottom of a glass, flatten ball to form a 2-inch round. Repeat procedure with remaining balls, leaving approximately 1 inch between flattened rounds on baking sheet. Bake at 350° for 10 minutes or until lightly browned. Cool on a wire rack.