Cook the pasta according to the package instructions until al dente. Drain and toss with baby spinach in a large bowl until slightly wilted.
Prepare the other ingredients by chopping the basil, dicing the red onion, halving the cherry tomatoes, and draining the sun-dried tomatoes from their oil.
In the large bowl with cooled pasta and wilted spinach, add chopped basil, diced onion, julienned sun-dried tomatoes, halved cherry tomatoes, shredded parmesan cheese, and mozzarella pearls.
In a separate bowl or jar, whisk together the olive oil, reserved oil from sun-dried tomatoes, balsamic vinegar, minced garlic, Italian seasoning, pepper, and salt until well combined.
Pour about three-quarters of your dressing over the pasta salad mixture and toss gently to combine all ingredients thoroughly while reserving some dressing for later.
Cover your salad and chill it in the refrigerator for about 30 minutes before serving to allow flavors to meld together beautifully. Just before serving, give everything another gentle toss with any remaining dressing.