In a non stick pan on medium heat let the butter or olive oil get hot.
Add the potato, jalapeno and garlic. Let it cook for a minute without touching. Add the cumin powder and smoked paprika and toss gently to coat the vegetables. Let it cook for another minute.
Add the black beans and salt and pepper. Let it cook just to get warm for another two minutes. Taste and adjust the salt and pepper and spices to your taste.
Take the pan off the heat. Place 4 small or two large tortillas on two plates. Pile the filling evenly onto one half of the tortilla. Sprinkle a bit of cheddar cheese on top if using.
Now, with the filling side facing you, fold the left and right sides of the tortilla over the filling and then, working from the side closest to you, gently roll the tortilla over to create a tight roll.
Slice it in half and serve it with salsa on the side and cilantro leaves sprinkled on top.