In a mixing bowl, combine chicken breasts with 1/2 cup of onion, lemon juice, olive oil & spices, then add the thyme before adding the salt to taste.
Stir well & then let marinate, covered, in the refrigerator for about 3 hours, stirring occasionally.
Preheat oven to 350 degrees F, then place chicken breasts in a roasting pan & bake for 25-30 minutes or until done.
Remove from the oven & shred the chicken into slivers.
Open oval pitas at the seam to create a large pocket, then spread a tablespoon of garlic sauce on the bottom half before filling each pits with equal amounts of sandwich ingredients (i.e. chicken, tomato, onion, gherkins, mint & parsley).
Wrap the bottom of the 'sandwiches' with a napkin & serve immediately.