In a Dutch oven or a sauce pot, heat oil over medium high heat. Add the garlic, onion and ginger; cook, stirring often, until translucent and fragrant, about 5 minutes. Add tomatoes, cook, stirring occasionally, until soft, about 5 minutes. Reduce heat to medium-low. Add the tomato paste, stirring constantly, about 3 minutes. Increase the heat to medium. Add the chicken and cook, stirring often, until the skin begins to turn slightly brown and the fat renders, about 5 minutes. Add cumin, turmeric, ground fennel, red pepper flakes, stirring constantly, about 2 minutes. Add the chicken broth, water, coconut milk, chickpeas, Russet potato, carrots, bell pepper and sweet potato. Bring to a boil and simmer, stirring occasionally, about 10 minutes. Add the spinach and stir to combine. Add salt, to taste. Remove from heat.