Set water to boil (add a pinch of salt before adding pasta) and cook pasta according to package instructions (12 minutes). BEFORE draining, scoop out a cup of the starchy cooking water (a coffee cup works great for this!) and reserve until sauce is ready. The starchy water can be used to add to the sauce if it becomes too thick.
In the time it takes to cook the pasta, make the sauce. In a large saute pan (large enough to toss the pasta) over medium low heat, combine pesto, cream and milk and simmer to reduce for about 10 minutes while the pasta is cooking. Add optional add-ins (see notes below) to warm during this 10 minutes.
Toss pasta well with the sauce and Parmesan cheese to coat. Add a little of the reserved starchy pasta cooking water if the dish becomes too dry. Serve with extra Parmesan cheese.
**Optional Add-Ins** Add cooked chicken, shrimp, or sliced Italian sausage to warm through in the sauce. These can be cooked separately on an outdoor grill, in a cast iron skillet, baked in the oven or leftovers work great. Add chopped tomatoes to the sauce while it simmers. If you want to add veggies that need to be cooked first, start by sautéing them in olive oil (like zucchini or bell pepper), then add pesto, cream and milk to simmer and reduce.