Heat the oil or water in a large pot over medium heat. Add the onion and garlic and cook for 3 to 5 minutes to soften, stirring occasionally. Add the sweet potato, coriander, paprika, thyme, cumin, red pepper flakes, and salt and pepper to taste. Add the tomatoes with their juices, chickpeas, and broth, and bring to a boil. Reduce the heat to a simmer and cook for 10 min