Pour the olive oil in a large pot over medium heat. Add onion and cook until soft, which is about 5 minutes. Then add the garlic and cook until fragrant, about 1 minute more. Add the broth and bring to a boil.
Meanwhile, in a medium bowl, whisk together 2 cups water and the masa harina until it's smooth. Add it to the pot, whisking constantly until no lumps remain.
Next, add the enchilada sauce and Velveeta, and stir until the cheese is melted. Stir in the chicken, chili powder, and cumin, and simmer on low heat for about 30 minutes. Season with salt and pepper.
Serve hot with your favorite garnish and toppings.