OPTION #1
SL: Buy 1, get 1 half off!
PH: Enjoy your favorite appetizer and get half off a dessert now through [DAY].
OPTION #2
SL: Get ½ off dessert tonight!
PH: When you enjoy an appetizer, get half off any dessert!
OPTION #3
SL: Appetizer or dessert?
PH: Get both and take 50% off dessert!
OPTION #4
SL: Savory or sweet?
PH: How about both! Get 50% off dessert when you enjoy an appetizer.