Rub pork chops with the 2 tablespoons mustard and sprinkle with lemon pepper. Grill over hot coals for 10-12 minutes, turning once. Remove from grill and set aside. Arrange butter lettuce on four dinner plates; topping with sliced beets and onion. Slice pork chops into 1/2-inch slices and fan on top of each salad. Whisk together olive oil, lemon juice, dill weed, the teaspoon of mustard and salt and pepper to taste. Drizzle dressing over each salad and sprinkle with goat cheese and walnuts.