Step 1: Cook the pasta according to package directions in generously salted boiling water until al dente. Drain well and rinse with cold water to cool completely and prevent sticking.
Step 2: (Optional Glaze) In a small saucepan, combine balsamic vinegar and sugar (if using). Bring to a simmer over medium heat, then reduce heat to low and let it gently simmer for 5-7 minutes, or until slightly thickened. Set aside to cool.
Step 3: While pasta cools, halve the cherry tomatoes. If using larger fresh mozzarella, cut it into bite-sized pieces. Gently tear the fresh basil leaves into smaller pieces.
Step 4: In a large mixing bowl, combine the cooled pasta, halved cherry tomatoes, and fresh mozzarella balls.
Step 5: Drizzle the mixture with extra virgin olive oil, then season with salt and freshly ground black pepper. Toss gently to combine all ingredients.
Step 6: Just before serving, add the torn fresh basil leaves to the salad. Toss very gently one last time to incorporate the basil without bruising.
Step 7: Transfer to a serving bowl. Drizzle with the cooled balsamic glaze (if using) and garnish with a few extra fresh basil leaves, if desired. Serve immediately or chill for a short period.