1. Cook pasta according to directions on package. Drain as well as you can, then toss warm pasta in a bowl with 4 Tablespoons pesto. Add 1/2 parmesan cheese, and toss together to coat the rotini. Cover with plastic wrap, and refrigerate until the rest of the salad is ready.
2. Prepare the dressing: whisk together mayo, sour cream, milk, and the rest of the pesto. Add salt and pepper. Taste and add salt if needed. Add milk to thin (to achieve salad-dressing like consistency).
3. Assemble salad: In the bottom of a large bowl, layer romaine, pesto-coated pasta, and then top with tomatoes, olives, and mozzarella. Drizzle with salad dressing (less or more, whatever is your preference). Sprinkle with additional parmesan, those gorgeous pine nuts, and serve.
recipe source: Pioneer Woman “Pesto Pasta Salad“