Slice the tenderloin into 8 pieces and pound till they're 1/4 inch thick. Place the flour on a plate.
In a shallow bowl, beat the eggs. Chop the parsley. In a separate bowl, combine the bread crumbs, parsley, 1 1/2 teaspoons of the salt, and 1/4 teaspoon of the pepper. Dip each cutlet in the flour, then in the beaten egg, and finally in the bread crumbs.
Heat 2 tablespoons of the oil in a large skillet over medium heat. Working in batches, cook the cutlets until golden and cooked through, 2 to 3 minutes per side, using 2 more tablespoons of the oil for the second batch. Transfer to plates.
Meanwhile, boil the potatoes in salted water until tender, about 20 minutes. Drain and pat dry. Cut into 1-inch chunks. Return to the pot along with the cream, mustard, tarragon, the remaining salt and pepper and combine. Serve with the pork.