Preheat the grill to medium low, around 300°F. Prepare each naan on a baking sheet adding crumbled goat cheese to each flatbread. Add a 1/4 cup of mixed greens on top. Top with pieces of chopped prosciutto. Arrange half the nectarines slices on each pizza. Add cracked black pepper and drizzled honey to taste.
Place the baking sheet on the grill and allow the pizzas to "bake" until the goat cheese has melted and the greens have slightly wilted, about 10 minutes. Transfer the pizzas from the baking sheet to a cutting board. Drizzle each pizza with aged balsamic vinegar, slice and serve.