Steps

1. Peel the potatoes and cut them into small cubes. Boil them in salted water until they are almost tender, then drain. Chop the onion and sauté in butter for a few minutes and add the potatoes. Continue sautéing this mixture, stirring often, until the potatoes are tender and slightly golden, about 20 minutes. Season to taste with salt and pepper.
2. Warm the tortillas quickly, one at a time, on a hot griddle or pan. If you like, you may brush them very lightly with oil before warming. Be sure to take them off the heat quickly, or they will become crisp. They should be soft and flexible.
3. Put a rounded tablespoon of the refried beans on a tortilla and spread it across in a thick line down the center, almost to the ends. Add a heaping tablespoon of the potatoes, and arrange them, the same way, on top of the beans. Fold one side of the tortilla over the filling and roll it up, or if you prefer, simply fold the tortilla in half over the filling.
4. Just before serving, fry the tacos in a little bit of oil until they are crisp on both sides. Sprinkle them with hot sauce and chopped cabbage and tomatoes, and serve hot.