Beat first 5 ingredients at medium speed with a heavy-duty stand mixer until blended. Gradually add flour, beating just until combined. Chill dough 2 hours.
Shape dough into 4 (8-inch-long) logs; wrap each in plastic wrap, and chill 8 hours.
Cut each log into 1/4-inch-thick slices; place on parchment paper-lined baking sheets. Bake at 350° for 13 to 15 minutes or until lightly browned. Remove to wire racks to cool. Store in an airtight container 1 week.