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 1/4 teaspoon each of the salt and pepper. In a large frying pan, heat 2 tablespoons of the oil over moderate heat. Cook the pork, in two batches if necessary, until just barely done, about 1 minute per side. Remove the pork from the pan, let it sit for 5 minutes, and then cut into thin strips.
In the same pan, heat the remaining 1 tablespoon of the oil over moderate heat. Add the escarole, shallot, 1/4 teaspoon of the salt, and the remaining 1/4 teaspoon pepper and cook, stirring until the escarole wilts, about 1 minute. Add the broth and the thyme and simmer until the broth is reduced to 1/4 cup, about 3 minutes. Whisk in the mustard, cream, and the remaining 1/4 teaspoon salt; bring just to a simmer. Add the pork and any accumulated juices to the sauce, and remove from the heat.
In a large pot of boiling, salted water, cook the ziti until just done, about 13 minutes. Drain and toss with the sauce.