This recipe is an easy version of souvlaki on a bun. The toppings you add are up to you and shouldn't be limited to those in this ingredient list. I always say sandwiches make the perfect meal because of the variety you can add. Tzatziki is readily available in grocery stores; check near the deli sections. Or you can make your own by combining 1 cup (250 mL) plain yogurt, 2 grated cucumbers, 2 cloves of garlic (minced), 1 Tbsp (15 mL) vinegar, 1 cup sour cream and a bit of salt and pepper.