Cut the tenderloin in 4 medallions and each one in pieces of 1" inch cubes. Season with salt, half of pepper and soy sauce. Halved the onions and cut in slices. Peel and cut tomatoes in the same way, peel aji chilies and take their seeds out. Slice the green onions. Peel the yellow potatoes
and cut in half lengthwise, then cut each half into 1 each strips. Put the potatoes in a bowl with cold water to cover and swish to remove the surface starch. Drain and refill again, drain well, and pat dry in a clean kitchen towel. In a large frying pan, fry the potatoes. When they are ready, put them in paper towel. Using a large frying pan or wok over high heat, cook the meat. Add the pisco
and the high temperatures will evaporate the alcohol. Transfer to another plate. In the same frying pan, add the onions and aji chilies until the skin is nicely brown. Reserve. Then, stir fry the tomatoes with green onions. Reserve, in the same saucepan, fry the garlic and add sherry and wait until it evaporates. Combine everything and add the cilantro and parsley. Stir-fry. Serve with rice.