Cook the pasta following the directions on the package.
Drain the tortellini in a colander and rinse with cold water for a few seconds.
Let it dry completely, then toss with the spinach, garlic, tomato, mozzarella, and basil.
Stir in the oil and vinegar, and add the Italian seasoning.
Season to taste with salt and black pepper.
Chill until serving, and then toss well to redistribute the oil, adding a splash more if necessary.
Drizzle over balsamic vinegar just before serving.