Beat butter at medium speed with a heavy-duty stand mixer until fluffy. Add flour and next 4 ingredients, beating just until combined. Cover and chill 2 hours.
Shape dough into 2 (8-inch-long) logs; wrap each log in plastic wrap, and chill 8 hours. Cut each log into 1/4-inch-thick slices, and place on parchment paper-lined baking sheets. Sprinkle evenly with kosher salt, if desired.
Bake at 350° for 10 to 12 minutes or until lightly brown. Transfer to wire racks to cool completely.