Begin by preparing the creamy garlic toum. In a food processor, pulse together garlic, egg whites, and lemon juice until smooth. Gradually stream in oil while running the processor to emulsify and thicken. Season with salt to taste before transferring to a bowl.

In a large mixing bowl, combine lemon juice, tomato paste, ground coriander, and oil. Add the prepared toum and stir until well combined to ensure chicken thighs become tender and infused with flavor.

Slice chicken thighs in half lengthwise, season with salt, and place them into a resealable plastic bag with the marinade. Massage gently to coat thoroughly and refrigerate for at least 3 hours, or up to 12 hours.

Once marinated, remove chicken from the refrigerator and let it sit at room temperature for about 1 hour. Preheat the grill to a medium heat setting.

Thread the marinated chicken onto skewers, ensuring not to overcrowd. Brush the grill lightly with oil to prevent sticking. Grill for about 10 to 12 minutes until golden brown and the internal temperature reaches 165°F.

Remove skewers from heat and serve immediately on warm pitas, fresh pickles, and a generous side of the reserved toum.