Wash the chicken with cold water. Put a drop of white vinegar on your hands and rub it into the the chicken.
For the garlic sauce: In a blender or food processor blend the garlic, salt and cooked potato, adding the vegetable oil to the mixture while blending gradually. To thicken the mixture you can add yoghurt; about 2-3 tablespoons.
Add all the spices together with the 3 cloves garlic. Add the cooking oil and lemon juice and mix well with the yoghurt to make the marinade. Pour the marinade over the chicken and cover in a bowl and leave to marinade between 2-4 hours.
After at least 2 hours marinating in the fridge barbecue or grill the chicken pieces turning every 4 minutes until done. Rest for 5 minutes then cut chicken in bite size chunks.
Warm the pita bread in a toaster for 15-20 seconds only. Slice open with a knife sideways near the rim to make a pocket shape. Fill with chicken chunks then add the filling ingredients to each and finally top with the garlic sauce.