Directions

1. Preheat the oven to 250 degrees F. 
2. Wrap the tortillas in foil and place in the oven to warm up while you prepare the other components of the taco.
3. Heat the olive oil in a large, heavy bottomed frying pan over medium heat. Add the diced yam and stir well to distribute the oil.
4. Let cook, stirring occasionally, for about 8 minutes, until the yams are cooked through (watch them carefully to make sure they don't burn).
5. While the sweet potatoes cook, put the rinsed beans into a medium pot with about 1/4 cup water and heat over low heat until hot. Cover the pot and turn off the heat once the beans are heated through. 
6. Stir the onion, garlic, cumin and chili powder into the yam mixture, and cook for another 2-3 minutes, until the onion begins to brown slightly. 
7. To assemble the tacos, carefully remove the warm tortillas from the oven. Top each tortilla with a little bit of the yam mixture, a spoonful of beans, a couple of slices of avocado and a sprinkling of cilantro. 
8. Eat immediately.