Season pork with salt and pepper. Heat the oil in a large skillet over medium-high heat. Add the pork and parsley; cook and stir until pork is browned on the outside, and cooked through. Remove from the heat and set aside.
Make a bed of spinach on individual serving plates or on a large platter. Arrange slices of pear over the spinach. Top with the cooked pork and sprinkle with walnuts. Drizzle the balsamic vinaigrette over the whole salad.
Note: Place the pears in a lemon water wash (to prevent browning) if you are not serving the salad immediately after cutting the pears.