In a large bowl, combine yogurt, lemon juice, vegetable oil, tomato paste, yellow mustard, minced garlic, and spices. Whisk until smooth to create the marinade.

Cut the chicken into even 1-inch cubes and place them in the marinade, ensuring they are well-coated.

Cover the bowl and refrigerate the marinated chicken for at least 4 hours or overnight.

Soak wooden skewers in water for at least 30 minutes to prevent burning.

Preheat the grill to medium heat (350ºF or 175ºC) about 15 minutes before grilling.

Remove chicken from the marinade, thread 5-6 pieces onto each skewer.

Grill skewers for about 5 minutes on each side until golden brown and an internal temperature of 165ºF (75ºC) is reached.

Allow skewers to rest for about 10 minutes after grilling.

Serve warm with pita bread, garlic sauce (toum), and pickled vegetables.