Toss the chicken pieces with the curry powder, and set aside for about 20 minutes.
Melt the ghee in the pot over medium-high heat. Sauté the chicken pieces in the melted ghee until cooked almost all the way through, about 8 minutes. Add the onion and sauté until soft, about 3 to 5 minutes.
Add the diced sweet potatoes, chicken broth, kosher salt, and black pepper. Bring to a boil, reduce heat and simmer until the potatoes are almost soft, about 30 minutes. Stir in the spinach and cook about 5 more minutes. Serve in bowls with the quinoa, a dollop of low-fat or fat-free Greek yogurt, and cilantro leaves.