Cook the black rice according to package directions; cool.
For the vinaigrette, combine Dijon mustard, balsamic vinegar, extra virgin olive oil, salt and pepper in a small dish. Salt and pepper to taste.
Toss the cooled rice with the vinaigrette, but reserve a little for the end.
Add the tomatoes, olives, cucumbers and mozzarella cheese into the rice. Add chopped fresh basil.
Drizzle with the remaining vinaigrette, and add salt and pepper. Serve cold or room temperature. Garnish with fresh basil leaves.