Heat oil in a medium pot over medium heat. Add diced scallions, salt, and pepper. Cook until softened - about 3 minutes.
Add oregano or cilantro, cumin, and ancho chile powder together. Immediately add sweet potato and stir until potato pieces are coated in spices. Fry for 3-4 minutes, stirring frequently.
Stir in beans, water, and a few dashes of hot sauce. Bring to a boil, cover the pot, reduce heat, and simmer. Cook for 10-15 minutes, stirring every 5 minutes, or until potatoes are tender. While this is cooking, warm the tortillas for 30-60 seconds on each side in a pan over high heat.
Take the lid off the pot and cook for 5 more minutes to allow extra condensation to escape. Stir in lime juice and serve in tortillas.
Serve with cotija cheese, salsa, sour cream, and/or a squirt of lime.
This can also be served over cooked rice. To do this, skip the last 5 minutes of cooking with the lid off. This will keep the liquid in the pot, which will help to provide flavor to the rice.