In a mixing bowl, combine yogurt, lemon juice, minced garlic, cumin, coriander, paprika, turmeric, cinnamon, cayenne pepper, salt, and black pepper. Mix well to create the marinade.
Add the chicken thighs to the marinade and ensure they are well-coated. Cover and refrigerate for a minimum of 2 hours, preferably overnight, to allow the flavors to meld.
Preheat a grill or skillet over medium-high heat. Add olive oil to the skillet if using.
Remove the chicken from the marinade, shaking off any excess, and place it on the grill or skillet. Cook for about 10 minutes on each side or until the chicken is golden brown and cooked through.
While the chicken is cooking, prepare the garlic sauce by combining minced garlic, mayonnaise, yogurt, lemon juice, and salt in a small bowl. Whisk until smooth and creamy.
Once the chicken is done, let it rest for a few minutes before slicing into thin strips.
Warm the pita bread on the grill or skillet for about 30 seconds on each side.
To assemble, spread garlic sauce on the warm pita bread, add a generous amount of chicken shawarma, and top with cucumber pickles.
Roll up the pita bread and enjoy your Syrian Chicken Shawarma with Garlic Sauce and Pickles!