How to Make It
Cut the pork into 1/2-inch slices and flatten them with the heel of your hand. Sprinkle the pork with 1/8 teaspoon each salt and pepper and 1/4 teaspoon five-spice powder. In a large frying pan, heat 1 tablespoon of the oil over moderate heat. Cook the pork, in two batches if necessary, until just done, about 1 minute per side. Remove the pork from the pan, let sit for 5 minutes, and then cut it into strips.
In the same pan, heat the remaining 2 tablespoons oil over moderate heat. Add the carrots and sugar and cook, stirring frequently, until starting to brown, about 3 minutes. Stir in the scallions, garlic, ginger, and jalapeño. Cook, stirring, for 2 minutes longer. Add the broth, soy sauce, 1/2 teaspoon salt, and 1/8 teaspoon five-spice powder and simmer until the sauce begins to thicken, about 4 minutes. Stir in the pork and any accumulated juice and remove the sauce from the heat.
In a large pot of boiling, salted water, cook the fettuccine until just done, about 12 minutes. Drain and toss with the sauce.