Cook the chopped leeks in olive oil for 5 minutes until soft. Add the cilantro and mint and cook 1 minute more. Remove the pan from the heat and whisk in the yogurt. Season with salt and pepper, and add the lemon juice, if desired.
Pan-fry the sausage for approximately 10 minutes until nicely browned and thoroughly heated. Warm the pita rounds. Wrap the sausage in the warmed bread and top it with the sauce, shredded cabbage and onions, if desired.