Bring a large pot of salted water to a rolling boil and cook your pasta according to package directions until al dente. You want it tender but still slightly firm to the bite, as it will soften more as it sits in the dressing.

Drain the pasta and immediately rinse it under cold running water to stop the cooking process. This also removes excess starch that would make your salad gummy. Shake off the water thoroughly and transfer to a large mixing bowl.

While the pasta cools, halve your cherry tomatoes, dice the cucumber and bell pepper into bite-sized pieces, and slice the red onion very thin. Cut the pepperoni into quarters or small strips. Drain your olives well.

In a small bowl or jar, whisk together the olive oil, red wine vinegar, Dijon mustard, minced garlic, Italian seasoning, salt, and pepper. Taste and adjust the seasoning—it should be bold and tangy since it's flavoring all that pasta.

Add all your prepared vegetables, mozzarella, pepperoni, and olives to the cooled pasta. Pour the dressing over everything and toss gently but thoroughly until every piece is coated. Tear in fresh basil leaves and give it one final gentle mix.

Cover the bowl and refrigerate for at least one hour before serving, though two to four hours is even better. This resting time allows the pasta to absorb the dressing and all the flavors to blend beautifully.