Cook the pasta: Cook the pasta according to the package instructions until al dente. Drain and rinse with cold water to cool it down and stop the cooking process. Set aside to drain completely.
- Prepare the dressing: In a small bowl, whisk together the olive oil, balsamic vinegar, Dijon mustard, salt, and pepper until smooth and emulsified.
- Assemble the salad: In a large bowl, combine the cooled pasta, halved cherry tomatoes, mozzarella, and fresh basil. If using, add the black olives and nuts for extra flavor and texture.
- Toss with dressing: Pour the dressing over the pasta mixture and toss gently to combine, ensuring everything is evenly coated.
- Chill and serve: Cover the salad and refrigerate for at least 30 minutes to let the flavors meld together. Serve chilled or at room temperature, garnished with extra basil leaves if desired.