Cook the tortellini according to package instructions, adding the green beans and tortellini to the pot at the same time. While the pasta is cooking, make an ice water bath: Dissolve the salt in the warm water in a large bowl. Add 4 cups each ice and water and reserve. Drain the pasta, cool in the ice water bath for 2 minutes, then drain again and transfer the tortelloni to a large bowl. Whisk together the pesto and water and toss gently with the tortellini. Add mozzarella, sun dried tomatoes, and prosciutto and gently fold to incorporate. Season with salt and pepper to taste