Heat olive oil in a large pot over medium heat. Add the sliced onion and sauté until soft and translucent, about 5 minutes. Add the minced garlic and cook for 1 minute until fragrant. Season the chicken thighs with salt, pepper, shawarma spice blend, ground cumin, paprika, and cinnamon. Add the seasoned chicken to the pot and brown on both sides, about 3-4 minutes per side. Remove the chicken temporarily and set aside. Add the rinsed basmati rice to the pot and stir well to coat the rice in the spices and oil. Pour in the chicken broth and bring to a simmer. Return the chicken thighs to the pot, placing them on top of the rice. Cover the pot with a lid and reduce the heat to low. Cook for 20-25 minutes, or until the rice is tender and the chicken is cooked through. Turn off the heat and let it rest, covered, for 5 minutes. Fluff the rice with a fork and garnish with chopped fresh parsley. Serve with lemon wedges on the side for an added burst of freshness.