Storage: The yogurt dressing can be made up to 2 days in advance and stored in the refrigerator. It often tastes better after sitting for a while as the flavors deepen.
Substitutions: If you prefer a lighter option, you can use low-fat yogurt. Fresh herbs will provide a more vibrant flavor than dried; adjust quantities accordingly (use half the amount of dried herbs compared to fresh).
Variations: For a vegan version, omit the Gruyere cheese or substitute with a vegan cheese alternative. You can also add other vegetables like diced cucumbers, tomatoes, or red onions for extra crunch and color.
Tips: Use oil-cured black olives for a richer flavor, but regular sliced olives work well too. Make sure to drain any excess liquid from the olives before adding them to the mixture to prevent the sandwich from becoming soggy.