Step 1: Prepare the Marinade
In a large mixing bowl, combine the paprika, cumin, coriander, ginger, turmeric, allspice, and cinnamon, seasoning with 1½ teaspoons of salt and ½ teaspoon of pepper. Add the yogurt, minced onion, olive oil, and garlic, then stir well to combine. Set aside for later use.
Step 2: Prepare the Chicken
Pat the chicken pieces dry with paper towels. If using chicken breasts, slice them in half horizontally, creating one thicker, rounded piece and one thinner, triangular piece. Working in batches, place the chicken on a cutting board and cover it with parchment paper. Use a meat mallet or rolling pin to gently pound the chicken until it reaches a uniform thickness of ½ to ¾ inch. Be careful not to tear the meat while pounding.
Step 3: Marinate the Chicken
Place the chicken pieces into the marinade, tossing to coat thoroughly. Cover the bowl and refrigerate for at least 3 hours, or up to 24 hours, to allow the flavors to develop.
Step 4: Make the Tahini-Yogurt Sauce
While the chicken marinates, prepare the tahini-yogurt sauce. In a small bowl, combine the yogurt, tahini, lemon juice, and minced garlic. Season with salt to taste. Refrigerate the sauce for at least 30 minutes before serving. The sauce can also be stored for up to 3 days in the refrigerator.
Step 5: Preheat the Grill
Prior to grilling, let the marinated chicken sit at room temperature for 30 minutes. Preheat your grill to medium-high heat, or if using a grill pan, heat it over medium-high on the stovetop. Lightly oil the grates of the grill or the surface of the grill pan.
Step 6: Grill the Chicken
Remove the chicken from the marinade (no need to shake off excess) and place it on the preheated grill. Cook the chicken for 6 to 8 minutes on each side, or until fully cooked through. Cover the grill halfway through cooking if necessary to retain the heat.
Step 7: Serve
Transfer the grilled chicken to a plate, sprinkle generously with salt, and squeeze the lemon half over the top. Allow the chicken to rest for at least 10 minutes. Garnish with fresh parsley or mint leaves, if desired, and serve with the tahini-yogurt sauce on the side.