1. Whisk together balsamic vinegar and next 4 ingredients in a bowl. Stir in shrimp and next 4 ingredients. Cover and chill 8 to 24 hours.
2. Stir in desired amount of basil just before serving. Serve with a slotted spoon.
Note: We tested with Good Seasons Garlic & Herb Salad Dressing & Recipe Mix.