Process first 3 ingredients in a food processor until smooth, stopping to scrape down sides. (Mixture will be sticky.) Spoon mixture into a bowl; stir in walnuts. Cover and chill 5 minutes.
Divide dough in half. Shape each portion into an 8-inch log. Wrap in heavy-duty plastic wrap; chill 1 hour.
Slice dough into 1/4-inch-thick slices; place on ungreased baking sheets.
Bake at 350° for 12 minutes or until lightly browned. Store in an airtight container up to a week.