To a large bowl, add the cooked + cooled pasta, chopped chicken, celery, grapes, green onion and sliced almonds.
In a small bowl, whisk together the sour cream, mayo, milk, vinegar, sugar, salt and poppyseeds until creamy and smooth.
Pour over the pasta and other ingredients in the larger bowl, toss to coat.
Serve immediately. If you are wanting to make this ahead of time, you will want to make extra of the dressing because the pasta tends to soak up the dressing as it sits.
